If you mailed it in July 2020 it might still be in a pile of unopened mail. Mail piled up in trailers during the pandemic and the IRS is working on opening millions of pieces of mail. Did you actually talk to the IRS? When you mailed the return did you use a service that would track it--like certified mail--so you would know it got there?
Here is what they say about mailing a return AGAIN if you already mailed it.
Per the IRS website IRS Operations During COVID-19: Mission-critical functions continue:
IRS operational status and alternatives
Processing Delays for Paper Tax Returns: Taxpayers should file electronically through their tax preparer, tax software provider, or IRS Free File.
We’re experiencing delays in processing paper tax returns due to limited staffing. If you already filed a paper return, we will process it in the order we received it.
Do not file a second tax return or contact the IRS about the status of your return.