I do it in the other way - first turn on the Drone, than search the wifi , than connect with the wifi cellphone to Drone, than start the app and I dont have any trouble. Try this way maybe?
Im not able because I use different phone only for my Tello (my Old android device)- I use phone without SIM card only the wifi connection to Tello. The phone is in flymode too ?
Probably the simplist way to tell if the problem is the phone or the Tello is trying to make the connection using another phone. Your video seems to show you are connected to the Tello via the wifi so you should be getting video. The only thing that is different when I connect using my Android phone is I get a message saying I can't connect to the internet through the Tello wifi connection which is a confirmation that I am connected to the drone.