Having an issue using inventory items.

Hi. I can't seem to figure out how to use items like shell supply and health recovery that are in my #5 and #6 inventory slots.

They're visible in the lobbies, but when I get into a game room they disappear and pressing the 5 or 6 key does nothing. How do I activate and use these items?

I've only been playing union war. Are items not allowed in union war rooms?

Thanks.

They're limited to missions and quests.