I can't sign in to Zepp app, what should I do?

Check whether the username and password you entered are correct.
Switch the network from Wi-Fi to 3G/4G in Setting on your phone.
Clear Bluetooth Share data and erase app cache/data.
Reboot your phone.
If the above steps do not work, please uninstall the app, re-install it from the Google Play Store/App Store, and try again. If this issue persists, please write and submit your feedback from the Zepp app and send your ID to the customer support.