Proxy Error in Bridge 2020

Since updating to Bridge 2020, upon opening the program I get the following notification (translated from German):

Proxy-Error: An error has occurred while establishing an Internet connection via the proxy server in your network. Contact your network administrator.

What is really annoying, is that this message pops up again every 15-20 minutes. When I leave my PC on over the weekend, I have to click first "OK" for at least hundred times until all popups are closing.

In our company the Internet is blocked via Proxy and only specific ports/websites are whitelisted. We already whitelisted a lot of domains to get the Creative Cloud to work. After searching I found the below website and we also added all addresses listed here as well to our whitelist.

https://helpx.adobe.com/enterprise/kb/network-endpoints.html

However the error message still occurs (although only once now, before adding these domains it popped up twice each time).

It would be great to know the specific error. Maybe there is a log somewhere? 
Thanks for your assistance!

Tobias