I also just had the same issue. I was in the Lion’s Arch Overflow on the Dragonbrand server. I cannot interact with the chest, but it is open and glowing, and Tixx says he already gave me my gift. I tried with both my engineer and my guardian with no luck. I have also exited out of the game and re-entered, and that did nothing as well. I had plenty of room in my engineer’s inventory, and my mailbox wasn’t full, either.