Offizieller Kommentar
The first time you connect with the app it needs to be connected to the internet so it can register with DJI. That only has to happen one time per installation.
Is the aircraft working with that remote with the DJI app? If it isn't working with that it won't work with Map Pilot Pro.
Aside from any of that, it should connect fine. There are plenty of users that use a different remote for using iOS apps with the + model.