Responsive Adsense will not show up on your WBB forum if you just paste you Adsense code into an ad slot because there are no defined widths for those ad slots. I was able to get Google Adsense to work on my site by placing the responsive ad code from Google within divs like so:
Since I have my ads placed in the top and bottom content areas I made my width wide when defining them, you should adjust it for the sidebar area. Next I went to my ACP> Styles> List Styles> chose my default style and then went to Advanced Settings and added the following to the Individual CSS section:
CSS
#respad {
width: 740px;
}
@Media only screen and (max-width: 990px) {
#respad { width: 360px; }}
The above is working for me