White turns to black when Illustrator file is exported as a PDF

[eve_3934]

I've checked out other posts, but I can't find one that solves my problem. I'm working commercially, so I can't attach a screenshot as an example, but when working in a CMYK or RGB color profile, I have white shapes that show up white on Illustrator, but when I export as a PDF the white objects turn to black. I'm not sure what to do. I didn't used to have this problem until the last month or so, and have not made any significant computer/Illustrator program changes. Nobody else I work with has had this issue; if it helps, I have a 2021 Macbook Pro and Sequoia 15.1 macOS. 

[Doug A Roberts]

Can you share an example file?