1. Delete Tello 's app and reinstall it. 2. Forget Tello 's wifi on your mobile. 3. Reset its WIFI: Turn the TELLO on until its flashing yellow rapidly, then press and hold the power button for 5-8s until the led goes off, then reconnect after it auto rebooting. Chipmun3 and DinoBaldi. More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.