Speedometer Cable

So while replacing my voltage regulator my speedometer stopped working. From digging around I found my speedocable just hanging out behind dash (could see it through the radio hole). From everything I've seen it sounds like people are able to just push the cable into the speedo and it magically worked. So I must be missing something because I can't get my cable to hook back up. I can see the speedo bounce some while trying to hookup the cable but after fighting with it and thinking I got everything hooked up the speedo still doesn't work.

So is there something I'm missing here? Any tips on getting everything hooked back up?