Why is my imported mesh shaded BLACK

I only used ZbrushCore for the model, and Substance Painter for the texture. Looking around online says it might be a normals problem, but how do I solve that? The base mesh when imported turns black unlike my other models. I got no error message when I imported it? I’ve fiddled around with the import settings with no good results, I’ve had better luck with sending it in as an OBJ rather than an FBX

Shoved a light inside of fish, more visible but acts like its still shadowed. I found a low poly version of the fish mesh and it imports just fine but now i lose the texture map/uv the high poly had. not for sure what forum thread could help my issue?