You are trying to connect with the vehicle and get the message
"Can't access Bluetooth devices":
The message appears because the app is asking for the location permission (From Android M Google pushing the developers to request location permission to access Bluetooth devices.
You will find more information about that by pressing the following link: https://developer.android.com/about/versions/marshmallow/android-6.0-changes.html ).
To solve that follow the instructions (The settings menu could be different on your Android, it depends on the version):
Search for the
"Apps" in your mobile settings.
Search for the "OBDeleven" app in the list and
select it.
In "OBDeleven" app settings select the
"Permissions".
Turn ON the
location permission. After that the message "Can't access Bluetooth devices" will disappear.