PIN cannot be set up or changed

Select 'Settings' > 'Accounts' > 'Access work or school'.

If you find an office365.boku.ac.at account there, disconnect this account.

You should then be able to edit the PIN code again without any problems.

If it turns out that you need to sign in with a Microsoft account for certain applications, you can sign in to the application again at any time.
IMPORTANT: Instead of 'OK', please select 'Only sign in to this app'.