There are a lot of plastics out there.
I have done a couple of repairs on cracks.
I took a little piece to a local Plexiglas (I will just call it that) fabricator.
I found which solvent they sell that melts it.
I scraped, cut, or otherwise collected some of the plastic and mixed it with the solvent to create a "glue-like" consistency.
I put it on the pieces and "glued" them back together.
Good luck finding.
1. the right solvent.
2. the same, exact plastic - manufacturer scrap??
I did not need much so I actually found it on the faring in the form of molding ports - you know, extra points etc that things have when the molding is done - whatever you call it.
Then there was another plastic and the "good" (I thought) solvent would not melt it - had to get another kind. Expensive and VERY volatile.
Short working time too!!
IMO epoxy will not stick to plastic.
Maybe the Mfgr will give you a hint?