How to Access prior year online returns. But they usually only keep them for 7 years. So hurry to get 2016.
https://ttlc.intuit.com/community/prior-year-return/help/how-do-i-access-my-prior-year-return/00/27010
If you can't get the side menus to open up to access the prior year..... You need to start entering some basic Personal Info in 2022 for the side menu to open up. Just continue a little ways into 2022. I had to go though about 12 screens.
If you used the Desktop CD/Download program then the only copy is on your computer and not saved or stored online. So you need to make and keep your own backups.
Or request a transcript from the IRS
https://www.irs.gov/individuals/get-transcript
Or get a copy of your return using form 4506
https://www.irs.gov/pub/irs-pdf/f4506.pdf
I requested prior returns and received an email saying they were ready for download. But when I clicked that link, nothing. Took me to this page: https://accounts.intuit.com/app/account-manager/myData?dg=true&cardRedirect=myData&exp=access