NWA90AX Fails After Setup Wizard

I moved into a new house with ethernet wiring, so I bought a wired router and two NWA90AX access points.

I set up one of the APs in a temporary location so we could have internet access while we moved in. I went through the wizard and everything worked as expected.

When the time came to move the router to the wiring closet and connect the APs using the in-home wiring, everything appeared to be fine but any device that connects gets disconnected after a minute or so.

I reset the AP. Went through the wizard. Changed the admin password. When the wizard was complete, my connection dropped. A new secured SSID 'Zyxel' appeared but I've no idea what the password is. I went through this twice and both times got the same result.

I disconnected that AP and tried the second unit. Exact same experience.

I reset that unit a 3rd time and went the Nebula route, something I'd wanted to avoid. Similar experience.

Wired devices are all accessing the internet as expected, so it's not the router/modem/service provider.

What am I missing here?