"I even applied /gix and it still comes back empty."

That doesn't surprise me. Do you know what /g, /i and /x do? The /x is certainly going to stop your regex from working, since it ignores whitespace, which is a crucial part of your regex.

I'm guessing the problem is that the text includes newlines in between the two tags you're matching between, and the . metacharacter does NOT match newlines UNLESS you add the /s modifier to the regex.

Just tacking modifiers on all willy-nilly does not make a regex work.