Team Chat: unable to establish secure connection to zoom

Dear all,

beginning today in the morning the Zoom chat is not operational for our company.

Message in Team chat: "No internet connection. Please check your network" -> Internet is working, that is not the problem;
When viewing the certificate: "Error code 1: DigiCert Global G2 TLS RSA SHA256 2020 CA1 certificate is not trusted."

Mobile phone app in another network is also not working (the Zoom Chat)
On zoom status page there is everything operational. 
But it looks as if the certificate issue is the problem.

Anybody else faces this problem? And has (hopefully) a solution for it?

Thanks to all.

Zoom version: 6.1.11 (45504)