I just put in my Boston Acoustics GTA-1005 5-Chan amp. Wired it all to the new head unit, tested and confirmed all 5 channels are working properly. All of a sudden, the subs stop working. Thought it might be blown subs, but no they work fine when wired to, say, the output of a rear speaker. No blown fuses in the amp. Tested, the RCAs for the subs are fine. Power is going from the head unit to the amp, its just the amp output to the sub that isn't working.

Any ideas why it stopped / how it can be corrected?