Coloured glass works in Unlit, not in Lit

Temppe

Hello, I have come up with another issue. I suspect this one will be simpler to resolve than my last!

I created a simple master material for translucent glass. Blend mode is Translucent, shading model is Default Lit, lighting mode is Surface Forward Shading. I've parameterised the base colour and opacity, among a few others.

I created an instance and so far everything seems okay. I changed the base colour and the sample sphere in the material instance editor changed colour... but the static mesh in the main viewport didn't. I can't get it to change colour unless I change the viewport view mode to Unlit, then it works.

Would anyone have any thoughts? I'd be grateful for any help!