Help! IDK why I am unable to change the text in any Vector editable text effect.

T,

In addtion to what Mylenium said, if you have used Type>Create Outlines (or Object>Expand) the text has become simple paths, unrelated to the font and editability of live Type.

Or maybe the text consisted of simple paths in the first place, as is usually the case with stock artwork.

Sorry, but that's way too generic and doesn't make a lot of sense. The obvious question would have to be if the artwork is even editable text in the first place, so for what it's worth, a screenshot and an explanation of what you want to change, from where you obtained the artwork and all the technical info like version of AI and system info will be necessary.

Mylenium