If you connect a Bq Aquaris 4.5 (or any other model from bq) to your windows/mac/linux, it won’t show in adb, Android Studio or Xamarin.

The solution is to add the VendorID to a certain file. My VendorID is 0x2a47 and you can get yours from Apple Menu > About This Mac -> System Report -> Usb -> Bq Aquaris 4.5 -> VendorID.

Then append that Vendor id to the following file: ~/.android/adb_usb.ini. Restart your adb server and it should work.

sudo adb kill-server; sudo adb start-server