Iray doesn't recognise transparency (Substance Painter)

Texturing a water tank. Made a glass front for it. When I had the glass as PBR metal rough with alpha blending, it worked great in the viewport but low opacity parts came out black in the Iray render. That's an issue in itself.

Then changed the material to asm metal rough, same issue with the renderer showing black instead of transparency this time.
Also in the viewport with this new material, the transparency affects the back of the mesh when viewed through the glass at the front. From the back of the model, the outside is still fully opaque as it should be.

My main issue is the renderer not showing low opacity/high transparency.

I'm fairly new to SP and don't know code (yet anyway) so non-programming answers only please.