After you file

I e-filed my returns 2/16/20, accepted the following day. I received my State refund 3/21 and I’ve received the Stimulus payment 4/13.  My federal return status says “still processing”... I filed 1040EZ, single, no dependents, one W-2, well before the Covid crisis struck. I recently received a letter stating they needed an additional 60 days to review my return. No explanation, no dates, don’t call! After that, I will either get a refund, partial refund or no refund...I made $8,442 last year!