Cannot connect Orbi Outdoor Satellite (RBS50Y) to Orbi Router (RBR750)

Hi, I have just purchased an Orbi Outdoor Satellite (RBS50Y) that I absolutely cannot connect to my Orbi Router (RBR750).

Please note that I have tried over 50x in probably all sorts of configurations (incl. the tips given here). I have factory-resetted both the Outdoor Satellite and the Router, and put them right next to each other in the same room, without any other satellites or anything else. 

No connection whatsoever, tried many times.

Are these models compatible after all??

I cannot update the firmware to the Orbi Outdoor Satellite without being able to connect it to WIFI.

Thanks for your help!!