If you are trying to e-file your returns, you cannot, the Online 2021 version is shutdown for the season.  You will need to print, sign, & mail in your return.

How do I switch from "E-File" to "File by Mail" in TurboTax Online?

https://ttlc.intuit.com/turbotax-support/en-us/help-article/printers-printing/switch-e-file-file-mai...