Mesh becomes half-transparent and coloured black as if the normals are flipped
 

Title says it all.
For additional details, I will give you an image.

https://imgur.com/ZUMLvWE

Can someone tell me what happened and how to fix it? thanks.

I've seen this before for me it was a gfx card driver issue. Try a driver update

What version of Maya are you using?

graphics card update? it's odd. it happened only on this mesh and this mesh only. but still yeah I will do it.

I use version 2018.

Couple of other things to try

Assign a new material to it. Sounds weird but I've seen this work before.

Export it out of the scene and reimport it into a new one. If you want to upload the scene I'd be happy to tell you if it does the same to me in Maya 2020

All the best
David