Up until late in 2022, there were claims that 2021 tax returns had not been processed. Michael Devine from the Internal Revenue Service says there was a backlog, but that has been cleared up.
Devine says those wanting to know more about the backlog can find information on-line.
IRS Operations: https://www.irs.gov/newsroom/irs-operations-status-of-mission-critical-functions
If you have not received your expected refund from 2021 and have not been contacted by the IRS by mail, you should contact them. Call 1-800-829-1040. Have as much information about your return as possible when you make that call.