Conditions: Windows 10. My internet was flaky, I think because my Ethernet wired interface has a hardware problem. For instance, Chrome was very slow or would not load a website at all. Edge would load sites usually when in this condition. I do not know how, but it did.

When in this hobbled operational mode, if I clicked a PDF file in explorer, or an attachment in my email reader, Acroread would simply not start up at all. I'm sure the executable began momentarily because I could see a little spinner appear momentarily, but nothing appears on screen. No splash screen, no error message, and certainly not the PDF file that I needed to see.

I am guessing that Acroread wants to start up and go immediately to the internet to check for something. When that failed, Acroread gave up or crashed and did not continue to show the PDF file.

Although my system is somewhat unique (likely you did not test for this particular case!) it seems unreasonable to me that the reader would not open and display a PDF file because there is an internet problem. That exceptional condition should not cause the software to fail. Maybe it could display a warning or error message. If all that acroread is doing is checking for updates or something, that shouldn't even be done every time the program starts, and it certainly should not cause the main feature of the program to fail.

I eventually became so fed up with it that I uninstalled acroread and am using Foxit reader now. Maybe sometime I'll go back to Acroread.