When we left the the flat everything was working, I checked my travel schedule just before leaving.
I did reset the rooter a few times. Cause I had difficulties connecting to it with my iPhone. But when I manualy connected via my phone with the router everthing worked.
The info on your letter caused a bit of confusion, since you don't need the password but only need the wpa key and of course the Wifi networkname . The password is only needed to modify the settings for the router.
Maybe you need to reset the router again, to release the DHCP address leases so the router can give you a new address.