I found the mistake! You have to follow the correct connection order, then it works.
1. Activate the Tello app
2. Switch on Remote T1d ...
3. Click on the gear icon in the app
4. Connect Tello with Wlan
5. Remote T1d ... is connected and works !!!
6. I'm happy
Ok, thanks, got it working. It just didn't do what I expected. After touching the scan button I expected the flashing blue lights to stay solid, but they just kept flashing, so I thought They didn't pair.
Just user inexperience!