It looks like quite a few others received the same rejection. There are hundreds of posts to the "My return was rejected due to FED_Taxable_Inherite..." thread. It looks like most people just refiled today without doing anything and were successful.
For our return.
There is no inherited IRA entry in our 2020 return.
Husband has an 8606 form.
We both did a small partial conversion from traditional to Roth IRA.
Thanks