The IRS sent me a notice on my 2020 return saying I now owe taxes and reviewed and faxed in what I think is right?

If IRS says you owe, either

A) pay it. Or,

B) dispute it in writing.

If you call IRS they may be able to tell you why you owe at this time.

@TBPUCK123 

The CP2000 you most likely got  was auto generated by the IRS computers  and now a human needs to review/process your response which  will take a very long time to happen.  You can call the number on the notice to see if any progress on the response.  Expect the IRS billing computer to continue to auto generate bills for the unpaid balance due until the human in the process has a chance to "set the record straight" according to your response.