Basic query about software that can debug facebook code errors, or even fix them

I've a few facebook groups and pages and they all work fine with sharing whatever I want. But on my main page (last 24 hrs) whenever I try to share something all that happens is the share box pops up for a millisecond (no text) and simply vanishes. I've tried it in both chrome and firefox, and on different computers, cleared chaches, the lot; same result. It's a fully public page too, so it's not a security issue I would not think.

At the moment the only way I'm able gt a rough idea whats going on is using googles right cloick > inspect element, or firefox's comparable function, to see whats going on underneath the webpage. I'm not sure what I am looking for though, and presume there are better more bespoke software to debug things like this.

What software or plugins do you need to see what the code is actually doing as it executes? And hopefully highlight hangup points or show me where the issue likely is, because im totally stumped at the moment.

Thanks.