It's the connection between your Trezor Suite application and their servers. Are you able to connect to the backend after clicking on the connect button? If you're not able to connect, then your firewall might possibly be blocking Trezor.
I forgot to write, (I will update the first post). Everything happens in the Trezor Suite Win app. And when I click on connect, nothing happens again. After a few seconds, the countdown starts again. I'm not sure what kind of backend it is.
I will try it later on another device.
Otherwise, the Bitcoin wallet works flawlessly.