Tree bottom invisible?

In blender, the tree I’m using has a bottom side, however when in roblox, its invisible. Any help? Desktop Screenshot 2020.10.20 - (2)

Game engines typically render only 1 side of a face, so if the model has faces that should be visible from both sides, I believe there’s a way to do it by fiddling with normals, but instead if you want it super thin, just make faces on all sides of it but super close to each other.

Yeah, Blender has faces and they can be indicated using a tool in one of their many menus.
Search up “indicating normals in Blender version (whatever version number you’re using)” and also 'flipping normals in Blender version XX.X" on youtube tutorials.