Occassionally, for no apparent reason a user's profile gets corrupted and they'll be signed in with a temporary. You'll have to go into the registry and perform some cleanup and possibly not be able to salvage the previous user profile and will have to create a new one for the end user.
Step-by-step guide
- https://winaero.com/windows-10-youve-been-signed-in-with-a-temporary-profile/
- Try to correct the mapping using the instructions above in the registry first, otherwise follow the instructions under "The profile folder path is correct"
Related articles