when the PO is useless

I work in a project that is very complex.   Lot of math and finance analysis.

Stakeholders are expert users with deep business knowledge.   Developers ate actuaries or data scientist. 

As soon as I introduce them to each other, as a po, I'm out.

Development is basically made of one to one conversations, im not even invited. 

My attempt to create backlog and user stories are failing, as ther are are only placeholders saying that the dev is ongoing.

I cannot decide any priority, as the developers think that stakeholders have priority over me. Stakeholders/users, want everything they ask done on the fly. 

I can just listen and ask why are they late and inform my bboss.

Funny thing is that I was a mathematician myself, but my point of view is not considered useful. The scrum master is just doing cerimonies.

There is one guy that every day in the daily says: im working wit C.to implement the dashboard. Since 4 sprints. during reviews, I see something which I don't understand whether is working or not. The only user, declares himself happy and says that needs more work. If she leaves the company, I don't know what we achieved.

I don't understand what to do in this situation....