Pin8 on the receive radio should be set to "CSQ Detect," "Output" and "Low"
reference is here http://mymountain.blogspot.com/2017/08/how-to-program-motorola-m1225-radio-for.html
Side note, I have this set on both radios, so if I ever decide to swap the TX and RX radios they are both good to go.
Hope this helps.
I use the Motorola M1225 mobiles in my vehicles and also have a pair for my repeater. They are great radios and you can find them for a decent price on Ebay. Of course programming them can be a bit tough. The correct model number for the M1225 is M44DGC90E2AA. This is the 450-470 and 40W model with 4 channels