Chromecast having issues with DIR-615 REV C, SW ver 3.1 topic

Hi All,
I bought a chromecast few days ago and cannot seem to connect it to DIR-615 router. The Chromecast website says DIR-615 with SW version 5.1 is a compatible router but I have SW ver 3.1 in it. For my router's model (rev C0 this is the most recent SW version.

Any help will be appreciated.

Thanks.