WRXB215

Now the confusion likely comes from discussions of higher power radios like the KG-1000G 50 watt model. That radio can exceed the power draw capability of a lighter socket/power port and should be wired to the battery. When in doubt consult the manual.

Good point.. I only use that Times New Roman "real" LMR400, or whatever its called.

First, there are many different types of coax cables that people call LMR400. Some have a shield that consists of aluminum foil over copper braid. Some, like the M&P 10mm stuff have copper for both layers. LMR400 is the Kleenex of coax. 
Does it make a difference during full duplex transmissions?
Darned if I know, but I’m certain that this range problem isn’t because of LMR400.
I just read an older thread on another forum where a guy said “my company has several repeaters that work just fine with LMR400, but I’m looking at making a portable repeater and I want something more flexible.”
Immediately someone went into great lengths telling him not to use LMR400 for repeaters. 

Yah, there's your problem, right there..  Many of the "experts" I have seen posting stuff here really struggle understanding the difference between "will not work/does not work/is bad" and "may not work 100% the best".

75Feet of LMR400 from my VXR7000 gets me ~50 miles of farz, so I'd say LMR400 works just fine - Not "The best", but good enough for most normal people with low-power, non commercial installations.

You will need to get them from their club. Click here Texas GMRS Network 

What happens when you connect another radio up to the same coax and antenna and transmit?

This is what I wonder too.  If he’s getting 20 watts out after the duplexer (assuming the right frequency), the problem sounds like something to do with the cable and antenna.

I am assuming that you get the same notification as below when you go to COM->SET COM:

But it is a good sign that Device Manager recognizes the Prolific driver. Do a right-click on Prolific USB-to-Serial Comm Port (COM4) and go to PROPERTIES and post screenshots for the General tab and Driver tab.
What version of the Anytone CPS software are you running.  I will attach a copy of version 2.01.
And, since I know it works well with the Anytone, I will also attach a zip of the Radioddity v2.02 CPS software.
What version of firmware is installed: Power off, hold down V/M key and Power on - it will show "V2.xy at the bottom of the screen; turn off power
If these do not work, I am starting to smell a hardware problem.  
Are you still within the Amazon refund window? Will Hesenate swap it for another radio and cable? They should certainly send you the WCH chip'd USB cable instead of the problematic Prolific cable; to try first.
 
AT779UV_Setup_2.01.exe Radioddity DB20-G Programming Software 2.02_20210707.zip

Normally, I would totally agree.  That said, we only have eight 50W Simplex/Repeater channels on GMRS.  In an increasing number of areas, more and more repeaters and "nodes" are being added which pipe in inane chatter from all over the state and/or nation for much of the day.  This makes ignoring those setups less of an option when the garbage being piped in from elsewhere ties up half or in some cases, all of those eight channels.  If your own bike is using a repeater or 50W simplex to stay in touch with family or friends in your local area, riding it becomes very difficult when you have multiple repeaters or nodes that pipe in pointless chatter from around the country jamming an axe handle between your spokes.
Just sayin'...

There are many "771" antennas out there and I assume they all come from the same chinese child-slave-labor hut and just get different stickers.  I have tested several (maybe all) of them, and have never noticed any difference in reception that my ear could pick up, and only small differences in improved transmission farz compared to stock GMRS antennas.
The only time I've ever noticed 'real' difference was when comparing it to a UV-5R antenna which is not well-tuned for GMRS, and even then, the differences were not huge.

It sound to me like you have the "bad cable" for Windows 11; I will keep working on getting a driver for that cable for you.
Who was your vendor for your AT-779UV and can you contact them about a replacement cable? In the meantime I will contact my vendor.
In the meantime, do you have access to a laptop with an older version of Windows than 11? Do you have any other USB programming cables for any other radios?

At what step are you seeing that message?
That looks like you haven’t selected the correct com port in the settings for the CPS software and you’re trying to talk to the radio. 
Show us what your device manager screen looks like for your com ports, please. 

FCC rules allow your son to use your GMRS license, including when talking to you on GMRS.
Use your GMRS certified radio to talk to your son on his GM-15Pro either simplex or through a GMRS Repeater.
Then work with your son to get his Technician Ham License and then you can cross talk on 2 meters and 70 cms Ham bands, if that is important to you.

I seem to recall that it is contingent on the last weather alert channel you set it to is the one that looks for alerts. So if you are not set on one for your area you won’t get the alert. I was surprised one day when I got an alert having not ever received one before. Check pages 39-42 and 55.
[07: WX-ALERT] Weather Alert
Function: Enables and disables the weather alert. Sets the alert for the currently select- ed NOAA weather channel.
Options: ON/OFF Default: OFF
  

The weather alert feature scans the weather frequencies and listens for the "alert tones". If the Nation Weather Service / NOAA doesn't transmit a tone, the scan feature has nothing to trigger on.

Here’s a newer description of the enforcement process than the 2015 enforcement fines article you linked:
https://www.fcc.gov/sites/default/files/public_enforcement_overview.pdf
And it is possible that doing nothing, including not responding to an FCC letter, might work, depending on your circumstances. It’s also possible that could result in what the FCC calls “an upward adjustment.”
I agree that a person should do their own research.  Your original post just came across as bravado and bluster and dismissive of ongoing discussion about the process. 
 

Actually it should say “This post is one person’s opinion. If you take legal advice from some random internet expert you’re on your own.”

Dude... It's right there in the manual.. I highly suggest you read Page #21
 

If they were not certified for GMRS use at that time they could not be considered “grandfathered”. 
If they don’t operate on the frequencies and at the powers listed in 95E, they’re not GMRS or FRS compatible.
If you configure them to comply with part 95 you might be able to get away without anyone ever knowing, but technically you would not be “legal”.
 

@WRQC527 I'm out of reactions but as soon as the time elapses, I'm going to like that post. 👍

You should probably say something like this as a preface to your post.
"The information contained in this post is provided for informational purposes only, and should not be construed as legal advice on any subject matter. You should not act or refrain from acting on the basis of any content included in this post without seeking legal or other professional advice."

Changing modes will delete all manually programmed channel information.
Have you been able to run the programming software in any way so as to be able to restore your previously programmed channel information?
At this point, your options to get the CPS programming software to work for you are possibly:
1) Install the WCH driver into Windows 11, per the zipped file I attached previously, and see if your cable works;
2) Run the CPS programming software in an earlier version of Windows starting from XP; 
3) Obtain the alternate cable that works in Windows 11 with the WCH driver; and/or
4) Obtain an alternate cable that works with the FTDI driver for Windows 11

Just curious: which mode is your 779 set for?  You can check by: while the unit is turned off, hold down the V/M key and power it up. Now you will be able to read the Mode and the firmware version number.
Mode will be something like: GMRS or (136-174)(400-470)
Of course, any mode will allow you to receive the MURS channels.

1st post here. I received my pair of UV-5R GMRS about six months ago. In my opinion, UV-5R GMRS + CHIRP = the ultimate value radio.
I think for those with issues, I believe the solutions lie within CHIRP. When I first received the radios, it wouldn't do this and wouldn't do that. But after experimenting with configurations I baked up in CHIRP, there is really nothing I don't think I can, or need, to do with this radio. My current programming has the standard GMRS, FM radio, and NOAA functions, and I also programmed in the standard ham frequencies for monitoring, as well as an emergency contact frequency, on which I enabled TX.
Radio-wise, I'm done. I moved on to antenna fun now.