Why was the federal tax return rejected?  If rejected for the 2019 AGI then try using a 0 (zero) for the 2019 AGI and e-file the 2020 federal tax return again.

what's the rejection message and code. if you post it in this thread we may be able to help. however, certain reasons for rejection cannot be corrected.  if the reason can't be fixed you'll have to mail in your return.  if the reason is AGI, sometimes the IRS database is corrupt. this would prevent e-filing