Hi Lotfi,
try this:
a) update your app at Android device - https://play.google.com/store/apps/details?id=io.robocore.app.prod
b) update bootloader on your RoboCORE - https://wiki.robocore.io/bootloader:flashing
c) if a and b doesn’t help, check another Android device
d) if c doesn’t helped - please send us code you uploaded to CORE2 (at community forum or at support@husarion.com)
Best,
Dominik