I just bought four announcer packs and four mega kill announcer packs from the Steam Community Market and decided to try it out. They work, but they don't show the captions for them on screen. Captions for Hero responses and the default announcer (and its mega kill counterpart) shows on screen, just not the custom announcers.

Is this something to do with the announcer packs not being bought in the Dota 2 Store? If not, how to fix this?
I've already verified the game's cache and it still doesn't work.

Thanks.