mo.unit blue - cannot be paired

Only the mo.unit blue can be paired with a smartphone.
It is not possible with mo.unit basic or mo.unit v.2.
Structurally, the mo.unit blue and mo.unit basic do not differ, only by the sticker.
The mo.unit blue has a silver sticker and the mo.unit basic a red one.

To pair the mo.unit blue proceed as follows:

Connect mo.unit blue completely
Install App on your Smartphone
login or register in the mo.ride app
Press + in the top right corner of the mo.ride app start screen
Click on unlock
Put on motorcycle
Connect the smartphone with the mo.unit blue as described in the app

Problems:
mo.unit blue is not found

Is the mo.unit blue already listed in the Bluetooth settings of the smartphone?
Is the mo.unit correctly connected to the battery?
Is the mo.ride app up to date?
Is at least Android 10 or iOS 13 installed?

The following things should also be tried:

Disconnect and reconnect the mo.unit blue from the battery
Uninstall and reinstall mo.ride app
Hard reset of the mo.unit blue (enter Setup menu, press and hold horn and start button for approx. 10 seconds)
Delete all mo.unit blue from the Bluetooth settings of the smartphone
Use another smartphone (To update the firmware)

mo.unit blue often loses the connection:
This problem occurs with older firmware versions of mo.unit blue.

Update the firmware of the mo.unit blue
Hard reset of the mo.unit (in setup menu, press and hold horn and start button for approx. 10 seconds)
Uninstalling and reinstalling mo.ride app
Update Smartphone OS

If none of this should help, please contact the motogadget support team.