To allow Notify app connect to your smartwatch the auth key code is required always
Only one app can be connected to your smartwatch at once, it means if official app connects to your smartwatch the connection on Notify app gets broken and viceversa
Once an app synced data from your smartwatch (steps, sleep, workouts, ...), all data get deleted from the smartwatch memory. This means an app cannot resync the data again. In other words, if you open the official app and data get synced, then the data will be lost on Notify app!
List of unsupported (not working) features:
Official app can be installed or not
Please check the proper Notify for Mi Band or Notify for Amazfit app on the PlayStore.
Check out the compatible Notify Lite for Smartwatches app.