I think you’re suffering from the same symptom as described in Loading...
The fix for this problem was only merged last week so it is not yet included in any LTS version.
Do you have a role or a user that has a $ sign somewhere? This might cause this problem. If you can get rid of that $ sign the it will probably work.
Which version of Jenkins are you using? Using the latest weekly should work, the fix is marked as lts candidate so it should be included in the coming 2.452.3 release.