Do you mean a 2019 tax return? 2019 cannot be e-filed after Oct 15, 2020.
A 2020 tax return cannot reject since it is too early to even file a 2020 tax return before Jan 31 2021 or later - the 2020 forms are not even ready yet.
If your 2019 return was rejected the only way to file it now is to print, sign, and mail it,
When you mail a tax return, you need to attach any documents showing tax withheld, such as your W-2’s or any 1099’s. Use a mailing service that will track it, such as UPS or certified mail so you will know the IRS/state received the return.
Federal and state returns must be in separate envelopes and they are mailed to different addresses. Read the mailing instructions that print with your tax return carefully so you mail them to the right addresses.