Can't access extender setup on WN3000RPv3

Trying to set up range extender connected via ethernet wire to a 5 port switch that's connected to a netgear router, but I can't access the extender setup page. The extender shows up on the network devices in the router admin when connected, but the internet basically doesn't work (<1MB/s download) on any device even when connected to the network either via wire or wirelessly. Speeds return to normal once the extender is powered off. I've tried hard resetting the extender and following the Netgear troubleshooting (which doesn't really cover a wired setup as it mentions setting it up near the router and then moving it to it's intended position... but it's wired so position doesn't matter.)