Hey @Trainer,
i ran into the exactly same problem here. With the help of this github error report I could solve my problem: [tado] Error when trying to add new Tado Home thing via PaperUI · Issue #7500 · openhab/openhab-addons · GitHub. The problem here was with the timeout on dns name lookup of auth.tado.com. My resolv.conf listed a non-existent dns server, so the dnslookup reverted to the second dns server in the resolver list and this took longer than 5 seconds. After i repaired my resolv.conf, the tado binding worked again. Hope that helps with your situation too.
Regards, Kai