If you are still waiting for your federal income tax refund from 2020, then you're probably not alone. The IRS has a backlog of over 20 million tax returns.
If you're waiting for a refund from 2020, then checking your refund status by using the official mobile app of the IRS, IRS2Go,is not going to help because it is limited to 2021 returns:
I used the app to check the refund status for someone I know who is still waiting for their refund from 2020, and I confirmed the app does not help. It simply gave me the following pop-up message:
Refund Status Error: Missing or Invalid parameters on the request
The only parameters are (1) Social Security number, (2) filing status, and (3) refund amount.
Even if you use the app to check the status of your 2021 refund, you might not find it helpful. Janet Novack reports that "a pitiful 24% of 'Where’s My Refund' users who took a survey last year found it helpful—down from 51% in 2019.)"
You can try calling the IRS, but you might not get a human. "The IRS projects it will answer 35% of calls this season—an improvement [from last year] but still not great," informs Novack. The app "can tell you that your return was received, or your refund was approved or that a refund has been sent. But it won’t tell you anything useful between the received and approved phase . . . ."
WSJ Editorial Board, The IRS Pleads Poverty, WSJ, Jan. 13, 2022 ("The IRS closed last filing season with more than 35 million unprocessed returns—nearly five times as many as in 2019 and three times more than 2020.") (Apple News link).