Hi @mlutolf, welcome to the Sonos Community!
I’m sorry to hear that you’re having issues with the Sonos app on Windows.
I’ve never seen any of our in-app messages ask for update verification before, would you be able to share a screenshot of what you’re seeing in the Sonos app? If you have installed the Era 100, I assume it’s up and running. If that’s the case, try remove the Sonos app from your computer and installing it again from our Downloads Page as this has the latest app version.
If you don't have the Era 100 setup yet (i.e. the light on top is flashing green when it’s powered on), then you’ll need to use a mobile device to set up the speaker. Once that’s done however, you can use the windows app to control your system.
I hope this helps!