At the beginning you're supposed to jump down to abaddon's reliquary. NPCs do their dialogue, and this is where the problem starts. They skip some dialogue lines and the game doesn't trigger next objective - investigate the ruins.
Taken from wiki, this is how it should look like. And below is how it looks like in my case.
https://ibb.co/hYZpjfp
Important note : This always happens with two or more people. It also happens when soloing, but sometimes it went through. Never with additional player. We restarted it like 20 times, tried multiple scenarios like only one person jumps, one person dies, both players dies, mesmer portal back to top, etc. Nothing worked. I don't know what causes them to skip dialogue, but once they do that it's game over.
Thought You might want take a look at that due to upcoming re-release of it.