I did a quick Google and there might not be enough voltage getting to the guns. I have no experience with this, though. Just thought I'd comment, in case it's helpful.
Thank you I did think of that. I’m gonna use the multimeter on that 5 V line going to the gun and see what it’s at.
I would advise replacing both edge connectors. The ones on a Jurassic Park III I did work with not too long ago felt rather loose (right one especially felt like it could fall).