You are too late to amend a 2020 return in order to get a better refund, if that is what you are hoping to do. You do not "amend " a return that was never filed in the first place. Amending is only done if you filed an incorrect or incomplete return and the IRS accepted and processed it fully.
If you prepared a 2020 tax return and did not even file it, your refund has been forfeited and will not be paid even the tax form shows a refund. If you owe tax due for 2020, it is still owed with late filing penalties and interest.
A 2020 return cannot be e-filed. The only way to file it is by mail.