I have found a way to connect them and add them to the Nest app. I went upstairs with the protect which was connected and started to add the other ones. Because I also have a Deco in the bedroom theu could connect with the network and the mesh network of nest. I think the problem is the mesh networks messing up things. when you are out of a lot of wifi, deco devices a.s.o they can find each other. After adding them to the app the status in the app is oke, but they are offline in your home network, but still connected to each other, so alarms from one to the other should not be a problem.