A friend and I have been unable to trigger the Model Diplomat achievement. We've both tried cheering when Bangar yells "Let Tyria hear you!" and we've also tried typing /cheer @ for Bangar and nothing. Unsure if I need to cheer earlier, or what.
I'm also having issues with this event not spawning. It's now the only thing a friend and I have to do to unlock the griffon. We've swapped maps multiple times, but couldn't find the NPC anywhere. She's simply not there for us.