We originally had Adobe Acrobat Reader DC 2018.009.20044 installed on our Windows 10 machines. We recently updated to 21.1.20140.30039(21.001.20140) last week.
We have an internal site and we use IE11 mode in Edge for this. This site has functionality in which a PDF opens in a separate browser window. This worked fine before the update, but since the update, a blank grey area shows up instead of the PDF. If we refresh(F5), then it shows up fine.
I have tried to test the version in which this broke and it appears to be somewhere between 19.010.20064 to 19.012.20040 as it works OK in 19.010.20064 but not in 19.012.20040. I have seen other posts with the same issue but they didn't have a resolution.