You cannot e-file an amended 2021 return. It has to be sent in by mail. Sign it and date it in ink, and file it by mail.
Do not expect quick results from amending. It can take four months or more for the IRS to process an amended return.
You can watch for information here:
https://www.irs.gov/Filing/Individuals/Amended-Returns-(Form-1040-X)/Wheres-My-Amended-Return-1