Did you re-assign the DIR-655 running in AP mode a new IP address under Setup/Networking/Router Settings?
If so, any PC should be able to access the 655s web at using the new IP address, i.e. 192.168.0.50, if the 655 is connected to the main host router and all other devices are getting an IP address. Ensure the IP address and subnet mask and gateway are all on the same pool range as the host router.
Ensure you disable ALL other features like SPI, WISH, WPS, any Filters, DHCP and uPnP and the LAN cable is connected to one of the 4 ports. WAN port is no longer used. If this has been done, access to the 655 running in AP mode should work and access to its web page.
Check the cable to ensure it's working properly as well between the main host router and 655.