Some polygons of my character are not showing when rendering (mental ray)

[Anonymous]

Hello, so I've been working on a project but for some reason one of my characters have this problem when I render (I'm using mental ray), specifically the neck dissapears in the render, but it works well when animating, I have no clue why is this happening.
(It's only a problem with this character in particular, not the render settings)

I'm working with maya 2016 on windows 10pro, GeForce GTX 1660 Ti

(I don't know how to post a maya file, that's why it's not added)

[damaggio]

Hi Cesar, mental ray no longer exists, you should start learning Arnold, it’s much more friendly and faster.

[Anonymous]

Is primary visibility checked on those polygons in their attribute editors

[mspeer]

Hi!

To attach a Maya file, please ZIP it first.

[sazoman]

Check if the faces are facing the correct way "Display Face Normals" and "Display Vertex Normal" then set the soft/hard threshold angles. Then delete by type history.