Are you looking in the right place in your inventory, alphabetically speaking? They're "Glorious" coffers, not "Stupendous" like the Jester's Festival golden coffers, nor "Anniversary" like the purple coffers.

Edit: Also, remember that you get only one per day per account per server, so all of your alt characters will only get purple coffers even if it looks like they're going to get a golden coffer (assuming you already got your one daily golden coffer on another character).

Were you in IC? https://forums.elderscrollsonline.com/en/discussion/655803