If your MX3 suddenly stopped connecting to your smartphone, the bluetooth function of your MX3 most likely froze.
To be able to start a Bluetooth connection again, please press the button until you see the pairing animation.
Wait until the display reads "fail."
Briefly press the button once in order to establish a new connection.
You should now be able to synchronize the tracker with the VitaDock+ App again.
By following the instructions in the app you are now able to synchronize your tracker again.
You don't have to make any changes to the settings of the VitaDock+ app.
Should the problem continue to exist, please contact our support and describe the issue.