I am using Mac OS Mojave (OS 10.14) with Illustrator 19. When I try to create a new file or open up an existing one, nothing happens! No new artboard appears for me - the page that loads on start up remains there. I've been using Illustrator since the early 90s and nothing like this has ever happened. This is a recent manifestation since the installation of version 19 - please advise what to do!