Your mother's tax return was not rejected because of a 2021 death. The problem (which TT will neither fix nor acknowledge) is that TT incorrectly transmits the AGI info in this situation, resulting in a rejection.
You can either file a paper copy or use a different tax program to efile. HR Block has the same bug, but others can do the job. I can't stand filing by snail mail, so I switched to FreeTaxUSA, and my tax return with the exact same info as the TT return was accepted within minutes.
If you search this forum, you will find many people filing for a deceased person having this same problem and using the same solution. Most of these other programs are free: Give them try.
