Beginner help- missing inside face from model

I have imported a model of a cone, made some adjustments and exported the model for use in after effects. The inside face of the cone is missing or invisible. How do I create the inside face?

I realize that this is probably a very simple thing to fix but I can’t find the answer anywhere. Thanks.

If there is an option in AE to use double sided faces use that.
In blender add a Solidify Modifier to your object with an appropriate thickness value, apply the modifier and export again.