I have the latest Adobe PDF reader installed on a window 10 64 bit machine. I am forced to still use IE 11 for many reasons What's happening when I try to open a PDF It tries to open but I get the following error: The is a problem with Adobe Acrobat/Reader. If it is running, please exit and try again (0:521). I have a few users with this issue and other than refreshing the page I can't think of anything that would fix this issue. It's enabled in the add on in IE. We tried uninstalling and reinstalling and that doesn't work either.