Can't update DNS settings

[frumbert]

My network has stopped working completely because my DNS server has died (disk crash, unrecoverable).

https://support.google.com/googlenest/answer/6274141?hl=en provides details on how to change the DNS served by the Nest router. The document provides no troubleshooting information.

In my Home app, when at advanced settings > DNS settings if I change anything, it spins for ages then says

Error

An error has occurred while updating your DNS settings. Please try again in a few seconds.

I am unable to  change the DNS server at all. How can this be resolved?

[David_K]

Try unplugging the cable from the WAN port (globe symbol) on the back of your primary Wifi point. Then open the app and see if you can change the DNS settings. Once updated, reconnect the WAN cable.