I spent several hours over the last couple of days on this one. I thought I would share in case anyone else has this problem. I created a kern feature in FontLab, but upon export the kerning wouldn’t show up in either OSX Cocoa apps or the Adobe apps. When I reimported the exported fonts in FontLab, the kern feature was still there. The solution? For some reason the system wouldn’t show the kern feature unless I added another feature, in this case a simple ligature feature. Go figure.