Hey in the documentation it says to use this with PPFX you need to use this function:
"screen_transition_set_render_surface(ppfx_get_render_surface(ppfx_id));"
However I had to use
"screen_transition_set_render_surface(ppfx_id.GetRenderSurface());"
I'm sure this is just because PPFX was updated, thanks for the great assets.