Just ran though it. Button pushed, no batteries, no atty, DOINK.
No button pushed, no batteries, no atty, no doink.
Button pushed, no batteries, with an atty, DOINK.
Button not pushed, with batteries, mod off, batteries start charging on screen.
Button pushed, with batteries, no doink.
If you're able to charge with a cord you should be plugging in. (And the above was done with my whittled down USB cable.)
If you're able to plug in and charge, it would have to be your pushing - instead of +, your + push isn't registering (does your + work to adjust, I would assume it does), you have batteries in, or you have something faulty that isn't allowing it to register.
Faulty could be the mod or your computer (USB port would be my first guess, try a different port, yes they can be picky about what you plug in where). If you can try another computer and can't get the connecting sound then it would almost have to be the mod.