Have you contacted Mitsubishi for suggestions since it seems to be their product with the issue?
The requirement for WPS is outdated and incredibly stupid - there are many brands of WiFi gear out there that don't support WPS and due to the security problems with WPS I'd never recommend it be enabled anyway.
The Mitsubishi unit only uses WPS, Ive connected mine to a few different AP's, every one that had WPS and a good signal level it worked, They don't seem to like low levels though.
Info is here
You will need a compatible WPA2-AES capable router with both WPS and 2.4GHz band enabled to use the Wi-Fi Control. Most WPS capable routers will be compatible with the Wi-Fi Interface. Every router has its own way of enabling WPS, and some routers have it disabled by default. Due to the large number of routers available, knowing how to activate WPS on your router is not something we or our installers are able to assist with, but is generally easily available in your router instruction manual. If your router is not compatible, it is possible to resolve this by plugging in an additional compatible router to your existing router.