Activation Links for new users not working anymore

I’ve tried it now and didn’t find any problem

Disable all other plugins and then try it. Also, use a default WordPress theme so we can determine the problem.

I must correct myself. The links are still not working. it seemed like it. so it is not caused by your plugin. Still investigating and trying to disable plugins which are somewhat related to emails or accounts.

When using the link the login/registration page shows without any message and user was not activated. no error either.

Links is like this: https://www.mydomain.com/sfo/my-account/?activate=2342346%3A%24P%25Hklhf987Hkfhis&suffix=yes

domain/code obfuscated