The IRS is seriously backlogged due to all the recent new tax laws and extra stimulus filings, as well as a few million unprocessed 2019 returns left over from the COVID shutdown. Contacting the IRS will not speed things up, and they have implored taxpayers not to call. Lots of other folks are still waiting (some 7 weeks or more), so please continue to be patient. See:
Tax refund delay: As tax season heads into the home stretch, some taxpayers are still waiting on the...
The IRS is under serious stress — what does that mean for your refund? (msn.com)
What led to IRS backlog: ‘Thin workforce,’ new pandemic relief programs | Federal News Network
Also, the letter from the SSA is based upon the 2020 W-2 info that your employer (not the IRS) provided them. They would have gotten that even if you hadn't filed your 2020 taxx return yet.
