** What do you want to achieve? ** export the model without failures
** What is the problem? **
when exporting the model has problems some parts disappear
EX:
picture in blender:
3.What solutions have you thought of so far?
change computer try other models uninstall and install roblox studio and nothing worked
It looks like you need to recalculate your normals.
Go into blender, select the meshes that are weird-looking, and press Tab+A. Once you do that, press Shift+N.
Like @alxzile said, recalculate your normals. If you do not know how to do this, find the meshes that are looking weird/deleting, press Tab and A, then press Shift+N to recalculate it.
In addition to the above advice (which I also agree that your normals just need recalculating), make sure that you have the Backface Culling display option enabled in the future so Blender renders meshes one-sided as Roblox does.
Thanks, it worked for me to recalculate your values
