Open Game I got a Brown vignette in Viewport

Development Asset Creation
1

When I started my level I got a brown brick vignette around the viewport. What happen and how do i fix it.

See images.

Thanks for your time.

Take Care

2

Usually happens if a post process material is broken.

3

Thanks for replying back and helping. Where is post process material and how do I fix it. Thanks for your time.