What worked for me was to e-file only my federal taxes first, and then back up in the software and e-file my state taxes. Trying to e-file both at the same time caused the "failed validation" error. My state happens to be California. I am using the desktop software for 2021, with Windows 11.
I did try the recommendations to uninstall and reinstall Turbotax, and to re-boot, but that did not work.
