SXR80 Nest Protect

A couple things to try. 

1. make sure icloud relay and private mac/ip address are disabled on the device you're using for setup. It can cause issues with some app setups. 

2. You can try disabling the AX mode on the SXR for setup. Some devices have issues with old drivers. Get them connected/setup (if you can), then update them and re-enable the AX to see if they'll work

3. Some devices have issue with WPA3 mode. Try either enabling wpa3/wpa2 mixed mode (if it has it) or just use wpa2 mode

4. Remove any special characters/spaces from the ssid/password. I've seen IoT devices with issues on those

5. Some devices do have issues if you're device doing the setup is on 5ghz while they're only 2.4ghz device. Tends to be devices that the coder was lazy on. If this is the case and the other options didn't work, what I've done in the past is shut off the router/satellites. Then turned a phone hotspot on with the exact same ssid/password as the router is using but having the hotspot on 2.4ghz. I get the devices connected/updated and then shut off the phones hotspot and turn the router back on. Works most of the time this is an issue. There's other routes to do it but I've used that method before. 

try those options.