Error 1108 indicates that the speaker has a problem connecting to the Sonos update servers.
Do you use a WIFI extender in your network?
Do you use a second router?
If any of the two are correct, remove the second router or extender.
If you do not have any additional WIFI devices, try hardwiring the Connect:Amp directly to your main router.
Hi @Fabian M
Welcome to the Sonos Community!
Sorry to hear of this issue you are having with updating your Connect:AMP.
If you are still encountering this issue, please try updating your Sonos system from a different controller, if you can - the Sonos app for macOS or Windows would be a good place to start. They can be downloaded here.
I hope this helps.