Sub won’t work after new deck install

I think I may be completely overlooking something obvious here, but I haven't installed a deck in a while so I'm feeling "rusty"

I just switched over my Kenwood KDC 2019 for an Alpine 9847 (YAY!) which of course as the separate sub preout. When my kenwood was in, the sub and amp was hooked up to the front outputs (since there was no preout on the Kenwood). Everything is hooked up on the Alpine except for the antenna, as I still have th purchase my VW antenna adaptor (this wouldn't make a difference, woud it?!), but the amp /sub is not working anymore. I'm wondering why this might be! I didn't rewire anything except for taking the RCAs out of the "front" output on the Kenwood and plug them into the Alpine's subwoofer output. (Everything else of course was swapped over too.) The deck works, plays CDs, I played around with the settings, the Sub out is on, bass turned up, etc.  ANY suggestions? Is there something ridiculously obvious that I am missing? Any suggestions would help, as I'd like to avoid taking it in and paying for someone to do it since MOST OF the time I have it all covered!

Thanks - looks like the problem has to do with the fact that the remote wire isn't yet hooked in through the antenna yet and this is what is causing the problem. I hope, anyways - since this would be an easy fix.

Sub amp trigger wire - where would this be? I had the sub professionally installed and so unless this wire is hiding somewhere, I don't know which one it would be as I've dealt with every wire that was hooked up so far...

Yeah, it sounds like the remote wire was clipped loose behind the deck when you installed the new deck.  More than likely it's a small blue wire.  Double check behind the deck, and connect it to the blue wire with a white stripe on the Alpine.