my Tello worked fine for 2 weeks than it required an IMU calibration but I'm not able to finish the process: at the third stage all is blocked and led on Tello became first orange than red than it shut down.
Tried many times shut down removed the batteries but nothingh always stop at stage 3!
Is it damaged?

Hey, sincerely sorry for late reply.  May I know if you put Tello at a level table and remove the propellers and prop guards before calibrating it?
If you're still experiencing this kind of issue, please do feel free to contact support at https://www.ryzerobotics.com/support
*****Calibrate IMU*****
1) Remove prop guards and propellers.
2) Power on Tello and connect Tello to your phone via WiFi.
3) Start Tello app, go to settings > more > calibrate IMU.
4) Please put it on the flat surface. You will have to put Tello in 6 different positions.