Background of the issue:
I am trying to resolve login issues for users with umlauts in their first or last names, specifically when logging in using the German language setting. This issue does not occur when logging in with the French language setting.
Symptoms:
Users with 'ä', 'ë', or 'ö' in their first name, last name, or nickname face login problems only when using the German language.
Questions:
Why do users with umlauts in their names face login issues only in German?
How can I resolve the login issue for users with umlauts in their names?
Hello. I am the developer of the site. I tested with the WPML plugin deactivated, and the issue does not occur. In other words, it works without the plugin enabled.
Thank you.
Please provide access to your testing site in the next private reply so that we can login and confirm the behavior with WPML deactive and with WPML active. I would test on my own test site, but I was not able to create a user with the umlauts in the username in a clean install without WPML active, so I can't test it.