Same issue with one of my users, it's device specific.
Uninstalled O365, reinstalled
signed out / signed back in, removed everything from windows credential manager
ran the https://aka.ms/SaRA-OfficeUninstall-sarahome tool also ran all the suggestions here: https://aka.ms/SaRA-OfficeActivation-sarahome
Still got error code 29 any time trying to activate the license for the user on their computer.
Solution: (this is heavy handed and time consuming, but the only option at this point:) backup the users profile, documents, desktop items, export browser settings, anything user specific. Log out of the user account as on as an administrator, go to the advanced tab under system properties / click settings under user profiles and delete the user profile. https://prnt.sc/u1yqhX_JlozW after the profile is deleted, log the user on again, a brand new profile is created and the Office 365 apps work. restore all the settings you backed up prior to deleting the profile.