If your DJI Osmo Mobile 3 isn’t working then you may need to activate the gimbal and install some new firmware to get it up and running. The issue I had was that the DJI Osmo Mobile 3 just had green and red lights flashing and it wouldn’t balance the phone. Before trying this, make sure the battery is fully charged.
To update the firmware you need to install the DJI Mimo app to your phone and have your Bluetooth switched on. You need to create an account to use the DJI Mimo app and register the device. Then from the app’s home screen it should tell you that a new firmware update is available.
Make sure you have your wifi switched on and then click on the firmware update. Then the firmware update will download to your phone. Click the ‘update firmware’ button once it is downloaded and let it run. Be sure to keep your wifi and bluetooth switched on and also to leave the app open. You want to try to keep your phone awake until the update is complete if possible. You will also want to place your phone in to the DJI Osmo Mobile 3 phone holder at this point
If you have one, screw a tripod or table mount in to the base of the Osmo Mobile. You need to place the camera of the phone in the direction indicated on the Osmo’s holder. Then try to slide the phone back and forth in the holder until it is level and not dropping on one side.
Once the update is complete, the DJI Osmo Mobile 3 will switch itself on and the red and green flashing lights will not be there anymore. You should see a solid green light and the gimbal will calibrate itself and balance the phone. To get the best results out of the DJI Osmo Mobile 3 you need to make sure you phone is roughly balanced before switching it on.
For reference, I am using a OnePlus 3 phone and the DJI Mimo app for Android.
Thats it! Hope that helped