Nest Wont Connect P018 Error, but I have no other Nest Devices

[jutteal]

Hello, I have been attempting to connect my Nest Protect to my wifi for the past 4 hours.  

I keep getting P018 which according to google means its an issue adding additional Nest Products.  The problem is this is my first Nest product I am setting up so I shouldn't been seeing this error.

For more info I have 3 Google Dots that are all unplugged and no other smart devices.

My router has pretty much all security features stripped off at this point and still no luck!

[cyphercat]

What I would normally try

1.  Set wifi to only 2.4GHz and switch off the 5GHz channel.  For some reason, most devices can only connect on 2.4GHz and I used to have the same Wifi name for both 5GHz and 2.4GHz channel so this eliminates one possibility

2.  If you have WPA2/WPA3 (Personal) security settings, don't set this on.  I was wondering why my devices kept disconnecting at regular intervals until I remembered that I changed this setting.  Now back on WPA/WPA2 (Personal)

That's all I can think of without knowing more.