FWIW, I tried using the web app to add my first SmartLife device. As previous occasions (with both the web and Android apps) I could not get it to accept my email or phone with the right password. I was about to give up when I decided to try using Chrome instead of Microsoft Edge.
Under Edge I was offered two region choices: International (tuyaus.com, I think) and China (tuyacn.com). Neither worked. Under Chrome it went straight to server tuyaeu.com and I got in!
I don’t think it’s a difference between the two browsers because they share the same engine. It might be because I have NordVPN active for Chrome, but not Edge.
Anyhow, if you registered for Europe, you might try changing the server manually if you don’t see the ‘Europe’ option.
Andy