[German]A German user pointed out a major umlaut bug in OneDrive that is causing problems for Azure users. Clients running Windows 11 25H2 cannot access OneDrive if the Azure username in the profile contains an umlaut.
Windows 11 25H2: OneDrive umlaut bug affects Azure users
German blog reader David R. contacted me by email on October 21, 2025, because he encountered a bug in OneDrive. On October 20, 2025, he noticed the really unpleasant behavior with Windows 11 25H2 during testing. An umlaut bug causes OneDrive (as a desktop service) to no longer work in the company's Azure environments.
The OneDrive desktop client no longer works
A OneDrive desktop client is used to access OneDrive content in Azure. The reader describes the Azure environment scenario as follows:
- For example, the Azure user has the name "Max Müller," which is said to be common in Germany—i.e., umlauts in the user name.
- The user folders in the profile under C:\Users\ are (apparently always) created as MaxMüller with special characters (for whatever reason).
Now the Windows client comes into play and problems arise. Until Windows 11 24H2, no service had a problem with the umlaut in the user name. Since Windows 11 25H2 has been used as a client, OneDrive Desktop no longer seems to work for users with umlauts in their names.
The OneDrive app cannot be started, but instead displays the error dialog "A problem occurred while signing in," and the user cannot sign in to their OneDrive storage.
Further tests: It is due to special characters.
During testing, the reader was able to narrow it down to users with special characters in their user folder. The issue can be reproduced in its environment on all devices running Windows 11 25H2 and with all versions of OneDrive (penultimate release and current Insider version). It appears that this "umlaut" problem has not yet been properly noticed.
Newly created Azure-only user throws error
In a follow-up email, the reader wrote that he then tested the whole thing again with a newly created Azure-only user named "Max Müller," who was then assigned the user folder MaxMüller in his profile, on another Microsoft 365-joined device running Windows 11 25H2.
Then the OneDrive wizard appears, asking where you want to save, and then it's game over with another error. So it is not possible to use OneDrive in Azure on Windows 11 25H2 if there are umlauts in the user name.
