Hi PietervanderEems-9280,
What do you do before this issue happened?
Does anybody else meet with the same problem?
To exclude the factor of Citrix Netscalar, it recommends you contact your IT admin to stop this kind of authentication for your account. Then try again.
If no luck, you could clear your client cache by the following command:
- Cache folder on Linux ~/.config/Microsoft/Microsoft\ Teams\ -\ Insiders
- To remove cache folder rm -r ~/.config/Microsoft/Microsoft\ Teams\ -\ Insiders