Hey! Thanks for the suggestion. I have just now come to the realization that, sometime over the last 3 weeks, Billboard GUIs aren’t working on heads besides the basic roblox head. I switched from the woman head to the basic head and, voila, the GUI showed up perfectly fine!
It seems to be a recent bug but I haven’t seen anyone bring it up in #bug-reports except for this one post (Nametag wont appear on users with different heads - #11 by stratolog).