I am still waiting on my refund from 2020. The IRS had a question, I uploaded a missing document to their portal - they said they never got it. Then I called

I am still waiting on my refund from 2020. The IRS had a question, I uploaded a missing document to their portal - they said they never got it. Then I called and was told they would release the refund as they actually had the document, but their software couldn’t process it - still nothing. I sent them the same ‘missing’ document to them again via certified mail months ago - still waiting.