I've had my Tello a few days and have not had luck with the Tello app. I have the GameSir controller and it connects fine. The Tello app started one time and crashed almost immediately. Is there another app that works better? I have an Android Samsung S9+ phone. Thanks!
The second one is a paying app. Both are really good and I use them over the official Tello app. Read into them and choose the one that fits your needs.
Also, try launching the Tello app without the controller. See if that works. If it doesn’t go to settings>apps and clear cache and data for the app. Usually that fixes most of the problems.