MR6550 won't recognize IPv4 Static IP device

Nighthawk is plugged into an unmanaged switch along with an IPv4 printer that is statically addressed. The printer will not show up in the Nighthawk's "connected devices" and will not route print jobs. If I enable IPv6, it shows in "connected devices" via NDP and works fine. If I switch to DHCP, it shows in "connected devices" and works fine. 

I would assume the Nighthawk would route LAN traffic even without being part of "connected devices", allow you to manually add a device, or recognize static addressed IPv4 devices on the LAN.