My 2021 tax return was rejected but it’s not telling me why it was rejected

[xmasbaby0]

The reason for the rejection is not important any more.    E-filing is permanently closed for past year returns, and any refund for a 2021 return has been forfeited.   If the return shows a refund, the IRS will not pay it.

If you owe tax due for 2021 (as shown on line 37 of the Form 1040) is it owed with late filing penalties and interest.  The only way to file a 2021 return now is by mail.   You have to print it, sign and date it in ink, and mail it in with a payment of the tax due as shown on the form, and then expect a bill later from the IRS for the additional amount owed.