im repairing my battery and attempting to fix side button

This sounds like it's an alignment problem. The thing about iPhone buttons (and most buttons in small electronics) is that you aren't actually pressing the button. You're pressing something that presses the button.

In the iPhone 12, the side button part is mounted to the bracket you're trying to screw in rather than to the bit you push to activate it. I took some pictures of a spare 12 housing I have under my microscope so you can see what I mean. The part in yellow is the actual button mechanism on the back of the bracket. The orange arrow is pointing to the little nub on the external button that pushes into it to activate. If they aren't lined up exactly correctly, the nub just deflects to the side rather than pushing the button. You'll also want to make sure your screws are tight so there's no give when the button is pressed.

Here's an overhead view as well so you can see what it's supposed to look like when it works properly. Same two parts, but installed correctly. I expect the little post near the button that slots into the bracket is to assist with alignment.