SSO Login not working

First off, hello everyone (this is my 1st post here)!

Since yesterday, I have been facing the following problem:

I access Zoom via SSO (account through my university, RUB in Bochum, Germany).

Now, I can only login on a "sporadic basis": Quite often,  I get the error "you cannot connect, please check your network and try again". 

However, my network-connection seems to be fine: I can access the www, emails etc. all up and running well - it is just Zoom that can't seem to connect.

FYI, I run a Macbook Pro (Mojave 10.14.6) via WLAN (Fritzbox 7360).

Since am dependent on Zoom working for my studies, any help will be greatly appreciated!

Thank you all in advance for your input!