I do have the repeater channel turned on. It is showing rp beside channel 21 and also has a plus sign above and display shows also, T and SQ
Hmmm. Based on your reply and confidence that you are using the equipment correctly, I am thinking a few things.
1.) It may just be that you are outside the usable range of the repeater. Some get a 30-40 mile radius, others only get 8-10 miles.
2.) I had two MXT400's (still have one) and they are not the greatest. If you are using the Midland antenna too, you are really doing yourself a disservice. I have gotten much better performance on 440 MHz than on the GMRS 462 and 467 MHz frequencies, which tells me the Midland antenna is tuned incorrectly. I replaced my midland antenna with a Comet multi-band antenna and doubled my range, just on that change alone.
3.) As others mentioned, while the upper frequencies are allocated for 25 KHz bandwidth, your radio is filtered down to 12.5 KHz. Both receiving and transmitting. The problem there is, wide-band carries more noise and the narrow-band receiver is filtering out half of the wide-band signal being transmitted from the repeater. Less usable signal and more noise means you are reducing your effective range.
Without being there with my equipment, its going to be impossible to help troubleshoot beyond the few comments I have already mentioned. For what its worth, I ditched the MXT as my primary GMRS radio because I was very disappointed in the the lack of meeting the advertised power ratings and the lack of bandwidth on the upper channels.