If that key is missing there should be no harm creating it. However it's not specific to a user, and you say you have one account working normally. But what is worrying is that if one key is missing, what else may be.

I suggest you create the key, restart, then try creating a new user. Log in. Does that function normally?

As a matter of routine, also download Crystal Diskinfo and post a screenshot of it Health tab showing SMART parameters to doa quick check on your disk.