AEG trigger not springing back when firing

I want to start off by saying, one, I'm sorry for asking a stupid question like this, I'm sure you all have much better things to do with your time. And two, I'm going to sound like a complete idiot, I'm learning. I recently picked up a cheap Lancer Tactical M4 style AEG and a M110 spring to replace the stock one with so it meets my field requirements.

Well long story short I opened the gearbox, messed up some stuff, but eventually got everything seemingly working again. However, when I was (for the fifth time or so) putting the gearbox back into the M4 shell, I broke the selector plate (out of all the things to break, I know). So, now when I fire the gun in semi-auto (can't switch it to automatic cause of broken plate), the trigger gets stuck in the "back" position and I have to press it forward to get it to shoot again. So, I have two questions:

1. Is that little spring on the selector plate doing anything inside the gearbox, and is the absence of it the problem here? Is it causing my trigger to not "reset" when shooting?

2. If not, what would be other possible causes? The gun shoots (at least it appears to) just fine, and when the battery is out the trigger springs back and forth perfectly fine. It's just right after it shoots the trigger doesn't reset itself for whatever reason.

I'm sorry for the long post, stupid question, and overall ignorance. Thank you in advance for any help.

Edit: Quick clarification, when I say I broke the selector plate, I mean it's broken in half at the arch.