NETGEAR Orbi 850 Series mesh has weak signal or dead zones

The checks in more detail

a white ring means a good link, amber a fair one and magenta none. A satellite at the edge of range gives the worst result, so move it closer to the router, about halfway to the dead room, until the ring is white, and then check the signal in the dead room. Position matters. Put satellites in the open, on a shelf or a table, at about head height, not on the floor, in a cabinet or behind a television, and away from metal, mirrors, fish tanks, microwave ovens and cordless phone bases.

Brick, concrete and metal-lined walls block signal more than timber walls. In a large or multi-story home, one satellite on each floor in line with the router often works better than one far away. If your home has Ethernet sockets, wired backhaul, where the satellite is connected to the router by a cable, is far better than wireless, since it frees the satellite's radios to serve devices. Check the devices. Old devices may hold on to the router's signal when a satellite is closer; turning Wi-Fi off and on moves them.

Make sure the system runs the latest firmware, since Orbi updates tune roaming. In the app, check that the satellite's ring is white after moving, and run a speed test in the dead zone. If you have too few satellites for the area, a second may be needed. Avoid placing satellites too close together, since they interfere. If one satellite persistently reports a poor backhaul even when close, restart it, and if that fails, contact Netgear with the serial number, since it may have a radio fault. A single dead corner may be better served by a wired access point than by a satellite.