Stuck in Cliffside Fractal...
This scenario just happened to my party. Thankfully, they were great enough to go through another round and we got through Cliffside again with no bugs.
I was the one to hit the final seal to break it (mesmer), and it seemed that the cultist healed the seal a little just as I broke it. There was a breaking animation, and the seal disappeared, but the top right showed a sliver of health remaining. The seal was invisible yet clickable. We broke it again but the gate did not open. The enemies also stopped spawning on both sides.
We did a mass-suicide and the seals respawned, but the enemies did not spawn at all so we had nothing to charge the hammer.
Again, note that we outright reset everything with the same people in the party and did Cliffside again. It worked fine the second time.
we just had the same bug, on our 3rd fractal. really annoying