hi Fabien, the netgears routers sometimes go into a weird state that can only be resolved with a ptp (power cycle) of the router itself. Did you already try that?
On another note: Behind the scenes I have been completely rewriting the Homey Netgear app. It brings an important new feature: a separate Homey device per device attached to your network. So phones can be added individually, and the presence detection can be much better optimised per device. It will also bring a very nice new function related to Homey V3 (I can tell more once Homey V3 is released)