Try your stock antenna outside your fairing. If that doesn't help I'd say you have a connection problem or a bad unit.
I bought the HD XM module for my 2008 Street Glide, it worked great with the antenna inside the fairing.
I transfered it when I traded for a 2009 Street Glide, it worked great with the antenna inside the fairing.
I then transfered it to a 2012 CVO Street Glide and the reception sucked so bad it was useless. Same unit, same atenna location couldn't use it.
I then moved the stock XM antenna to oustside the fairing and it is working better than ever.
It fits perfect between my windshield bags and can hardly be seen unless you just have your nose where it doesn't belong. lol