What can I do if my printed federal tax return never made it to the IRS?

For whatever reason, my spouse and I are not able to e-file our joint federal tax return. We've been mailing in our forms for the past 10 years straight. It's worked out so far, but takes a lot longer to receive the refund. This year, nothing new, except we haven't received our refund yet (and we filed back in May). We haven't thought too much about it, thinking perhaps it was COVID related. However today, I created an account on the IRS website to request a transcript. It says "No tax return filed" for our 2020 (filed in 2021)! We successfully received our state tax return, which was mailed out the same day. I've got to believe that our federal form never made it to its destination. What do I do?