What type of glue is best for plastic? What could work here?

[vybrano]

I took apart a seat.

I have to glue together some cracks in plastic cast. And then glue back vinyl to the plastic cast. (Cast is too old and cracks&brakes if I try to attach vinyl by stapler or even predrilled rivets)

Problem is, that nothing sticks to that plastic cast. I tried super glue, cement glue for PVC pipes, wood glue, epoxy glue, .hot glue gun...after hardening everything peel right of the plastic.

What type of nonexpensive glue could stick to it? The seat was already repaired and somebody used some kind of glue, that looks like it has a sand in it...no idea what glue it is, but it holds perfectly! What could it be?