Cannot click and drag to select/highlight text (or anything else) without holding shift, too, on Catalina

I'm trying to solve a problem with a new 13 inch MacBook Air running Catalina 10.15.6 where you cannot click and drag in order to select a line of text or seemingly anything anymore for an action like copy and paste unless you hold shift while you click and drag. The text or desired thing to highlight does highlight as you drag, but if you let go of the shift key before you let go of the mouse click, then the highlight will just disappear the moment you let go of the mouse click/trackpad clicker.

It happens in any text you can think of that you could highlight in any app on the computer. Pages, text edit, email, safari web pages, etc.

This is not my laptop but I connected to it remotely with multiple screen control programs and even using a mouse on my end, I could not help figure out why click and drag to make a selection wasn't working anymore either.

I have multiple macs with multiple MacOS versions and none of them have this problem. I've never seen it before on any mac and I can't figure out how to solve it.

Is there a specific corrupted plist that needs to be tossed that I don't know about?

Or a Catalina setting hidden somewhere that just needs to be changed?

It's a real head-scratcher.

Thanks for any help from those who have an idea of what's going on.