Can't change map provider in Tower


I can’t change the map provider in Tower. It only gives me google map option. See attached picture:

The same happens in the two devices I use:
1.- Cellphone Samsung Galaxy J5, Android 5.1.1, Tower v3.2.1
2.- Tablet Samsung Galaxy Tab 4, Android 5.0.2, Tower v3.2.1

I want to use Mapbox so any help would be very apreciatted.

Look’s if you can find here the solution: