Can anyone explain to me why it's not letting me glamour this hat?

I meet all its requirements, as the tooltip clearly shows.

wht's the level of the hat you're currently wearing?

if the hat you're currently wearing that you're trying to glamour it onto is below lv 72 it won't glamour onto it.

Yep, that was it. Figured it out.

Man, some of the systems in this game are annoyingly obtuse if you're not familiar with their ins and outs.