American hi fi AHF-630

OK, so I've been mucking around with this head unit all day. I own a mazda 323 protege (99) or a mazda "crapbox" as it's commonly referred to.
Purchased a cheap Bluetooth head unit hoping from we all know where, and connected it up this morning, powered it on and it lit up like a Christmas tree! Powered it down to insulate the connected wires, and the 2 12v wires crossed and blew the damn thing! So, the warehouse being good on their return policy, allowed me to swap it out for another one. I was careful in the installation and used a wiring block instead. All wires are hooked up as they should, but there's nothing at all coming through. Checked the fuses, and they all seemed fine, but replaced them anyway. However, I still have nothing at all. Any suggestions for a solution? I'm considering taking it to an audio shop, but thought id try here first. Thanks in advance, guys!