I have just found out via Insights that the Nest Protects - when the EAP is on the 1.2.0 firmware - are blocked by an ACL that I have not setup. When I rollback the firmware, this mystery ACL block...

@Hank21 Multiple times I've tried installing the firmware for my EAP615 Wall's, and each time that I do, the ability for the Nest Protects installed in my home to connect to the network begins to...

@MR.S That fixed it; thanks!

So. I installed the beta firmware - 1.2.0 and was trialing the Lock to AP feature. Unfortunately, I selected the Nest Protect in my son's room in error and it now it cannot get back on the network....

Excellent; added in the IP address of the AdguardHome Pi and it works perfectly. Thank you!

I have OpenVPN working on my ER605 and it is successfully setup so I can access it remotely and it will forward my remote connection via my ISP. I've set it up this way as I like to occasionally work...