I updated kirby from 3.3.5 to 3.4 by replacing the folder “kirby” in the root directory.
Now I can’t log in to the panel. Trying to login throws: “Call to undefined method Kirby\Cms\Language::title()”
The reuse of the old kirby folder still works.
Are there any known issues about this topic?
Additional note: I use 1 language (de) in this project. If I remove the subfolder “site/languages” login is working, but then the same error appears by creating or editing users inside the panel.
Have you deleted the media folder, Localstorage and the browser cache after updating?
Yep, just right now, but it does not help 
Don’t know what the problem was. Just started with a plain project installation again and added my stuff step by step. Everything is working now.
Same problem again now!
Userlist in panel is empty and creating a new user throws:
Call to undefined method Kirby\Cms\Translation::title()
Found a solution now.
Problem was an old version of “Enhanced Toolbar Link Dialog Plugin”.
Update to the latest version solves the problem.