Error occurs when user opens security settings

Hello, everytime my users try accessing the security page they always get an error and the page looks very weird. It doesn’t do it for me (admin) but everyone else. I made a copy of the page so you can see- http://v2202005120896117191.supersrv.de/dp-cloud-weird-error.html
I tried adding one of my users as an admin and the error still occured. Thanks!

Here is the error in the log- Error index Exception: Argument 1 passed to OCA\TwoFactorEmail\EmailMask::maskEmail() must be of the type string, null given, called in /home/cloud/public_html/apps/twofactor_email/lib/Provider/State.php on line 80

one more thing- I removed the two factor email provider app and it did resolve my problem by the app is essential so I need to resolve the issue without disabling it.