I’m having the exact same problem as most of the people posting here. When I talked to the Tixx character in the mists (I didn’t know you received different items in pvp areas) I didn’t receive anything (even though I had plenty of inventory space) and I wasn’t able to interact with the chest (which I hadn’t used at all prior). I went to Lion’s Arch and had the exact same problem, trying first in overflow and then in regular Lion’s Arch. In all cases Tixx said he’d already given me the present and I wasn’t able to interact with the chest. It looked like it was already opened even though I’d never used it before.