I am trying to configure an Archer C50 as an access point in an outbuilding connected to the primary router in the house (Archer A6) via ethernet.

I've tried very carefully following the instructions in this guide several times:  https://www.tp-link.com/us/support/faq/1199/

Every time after the step where I disable DHCP the access point stops providing internet to connected devices (unable to get IP) and it's web browser interface won't load from any point on the network, but it continues broadcasting WiFi with the correct SSID and password (just no internet), and the DHCP client list on the main router (the A6) shows the second router with the correct IP. The only way I've been able to regain access to the settings of the C50 is to do a full reset via the button on the back of the C50.

The ethernet cable goes from a LAN port on the A6 to the WAN port of the C50.

Assigned LAN IPs:

A6:  192.168.0.1 (default)

C50:  192.168.0.100

A6 DHCP settings, IP address pool:

192.168.0.2 - 192.168.0.99

The IP adrress of the C50 was initially being randomly assigned within the pool range despite setting the LAN IP manually on the C50. I reserved the chosen IP for my C50's MAC address in the settings of the A6, which did cause the C50 to be assigned the correct address when I connect it, but didn't fix the internet on the access point.

All other settings are set to default on both routers (I factory reset both just to be sure).

I've also tried messing with the order of the instructions, and using the "DHCP relay" setting instead of disabling DHCP, but nothing has worked yet.

Any idea what I might be doing wrong that could be causing this behavior? Is there any further information I need to provide?