The WiFi does not appear in any fashion in the router's lists. No DHCP table entry for the WiFi.
I see this in the log, when I try to connect using WPS. It goes through and obviously initially sees the WPS request.
May 4 19:52:22 rc_service: httpd 301:notify_rc start_wps_method
May 4 19:52:49 rc_service: watchdog 307:notify_rc stop_wps_method
It also thinks the connection was a success, from the WPS page.
However, when looking in the DHCP table, no connection for the WiFi, and obviously trace of it in the list of connected wireless devices.
Since WPS on this router works for every other WPS device I've tried, including the MTH WiFi unit, I have to conclude the problem is not on my end.