Sometimes this can happen. Sometimes it won't even connect to WiFi.
For this instance, I recommend the following possible fix.
Make sure app is latest version, may need to Uninstall and reinstall.
Make sure after that make sure latest firmware is installed on Tello.
After that is all good. Power off Tello. Restart phone.
Place phone in airplane mode. Keep Bluetooth off. It runs very close to same frequency of wifi for 2.4ghz and will cause interference. After that power Tello on
Wait for constant flashing yellow
Then turn wifi on smartphone
Open original Tello app and make sure it says connect to Tello, click connect and select Tello wifi then back out and it should load into flight feed.
You can not run video on two devices just FYI! If you run it on one device then disconnect device from wifi then immediately try another device it will have issues.