2020 Tax return refund no received

Back story:

I didn’t file my taxes for 4-6 years because of a letter and not knowing what to do. Fast forward to 2024 I decided to make sure I was squared away with all my stuff (luckily I knew I really only owed for one year). Regardless, I filed all my tax returns about the same time, one of which was 2020, I was due a refund of over $6,000.

I had someone doing the taxes for me and on the night of April 15th 2024 he emailed me and apologized because he screwed up my return and would not be able to complete it. So I went on freetaxusa and did it myself. I then rushed to staples to send it overnight via UPS.

Months later I received my return in the mail with a sheet with check boxes on it, saying I needed to sign my return. The 1040 was STAMPED April 15, 2024.

Fast forward to now, I have called once every few months to get an update and they still cannot give me one. It is still open, however one IRS person has told me it was after the deadline and she “just works here” and another said it’s still open and assigned but they’re saying it was received in May…

What am I suppose to do here? I have the tracking number from the night I originally sent it and it was definitely before May because I paid overnight shipping…. But it appears they’re going to try to say it’s after the deadline.