Microsoft Teams not connecting "We couldn't connect to the internet": env_check_error

Question

The Microsoft Teams Application for Windows 10 is showing the following error after entering the eMail-Address for signing in:

We couldn't connect to the internet. Try checking your connection.
desktop-[...]
Error code - env_check_error
Failed to connect to settings endpoint

I tried reinstalling the app, rebooting, adding the hooks.json, removing the Teams Folder in AppData, and some other hints. Nothing helps.

Answer 1

I checked the Teams log file and I saw it tried to connect to odc.officeapps.live.com.

I tried to ping this address, then it resolved to europe.odcsm1.live.com.akadns.net.

The IP resolved to 127.0.0.1.

We found out that our local company nameserver had a forward configured for europe.odcsm1.live.com.akadns.net (for another reason).

So the problem was found.