Grid comes on screen when using PDFs in PDF viewer

[PWCB2005]

It ususally comes on after a few seconds after opening a pdf.  I do not know how to remove it or how it came on suddenly.  Any help would be appreciated. Here is what it looks like.

[try67]

See: https://community.adobe.com/t5/acrobat-reader/screen-turns-to-black-and-white-dots-using-adobe-acrob...

[PWCB2005]

Thank you SO much!!