It's hard to say without really digging in, as there are a lot of variables. It could be the topspin widget but I'd think that is the least likely offender. My first thought is that it's your targeting. What interests and basic demo info are you bidding on?

Did you once say that this exact page was performing really well for you in the past? If thats the case it's almost certainly the targeting, or possibly the right targeting but the wrong copy for that targeting. Watch the Facebook ad training to see how a few tweeks to my copy took me from a 8% sign up rate to 28%. It may be an issue along those lines.

I always tell people that there are only a few things that can go wrong. Traffic, offer (squeeze page), marketing (email copy and sales offers). It's always just a matter of tweaking until you figure out what the issue is.

Let me know about your targeting when you get a sec.

There are still quite a few variables so it will require a bunch of testing to truly know whats up. 12.5% is something you can work with though. It needs to come up but it shows that things are working, just not enough.

A couple more things to look at...

1. What's you age demo? Try raising it to over 25 at least, possibly 30. Older tends to convert better, unless you are certain you are a young persons band.

2. What is your location targeting? Try keeping it limited to the US and Canada for now.

3. You might still need to play with your copy. It looks good to me, but we can't always predict what headlines will do best, (Though I would first play with targeting).?

4. Is there anything in Facebooks interest options for "trucker songs" or specifically music related trucking interests? Are there any famous artists, albums or songs that are "trucking songs".
 You might also explore "road music" or "road trip music" or something along those lines. But you might create a dedicated squeeze page and headline to speak to a slightly broader (more road music specific) audience for that.