Replace Vertex Colour Results Turing Black

I’ve applied some vertex colour to a banner flag model, which I will hook up the Simple Grass Wind Material Function. But Reimporting the model with vertex colour (from Maya), and ticking “replace” in the import settings. The vertex colour is applied, however, the result is now the model has turned black. It doesn’t seem to be the material as models using the same material haven’t turned black. I’ve imported the model with “ignore” vertex colour and it doesn’t turn black. It’s only when I select “replace” in the import setting, and once its imported, then selecting back to “ignore” the issue is not resolved, it’s permanently black. Any advice?

Maybe the normals are inverted