This has happened twice recently. Not sure if wifi was down at the time but it didn't reconnect until I power cycled this morning. @franz Is there some kind of device log you can look thru to find out what exactly happened?
You will need to reach out to firstname.lastname@example.org, sorry I can't help troubleshoot connectivity issues.
@goblue -- I didn't see any open support tickets from you yet, but your controller is currently online. Please don't hestiate to contact the support team if the issue continues. Out of curiousity, is your router's firmware up to date?