"Internet connection required"

Haven't been able to get on for several days. As soon as it opens a window comes up saying "Internet connection required. An Internet connection is required to open this app. Please connect to the Internet and reopen the app." I have checked and double-checked: there is nothing wrong with my Internet and this app is the only app having a problem. I've tried redownloading, clearing the cache, deleting all associated files, and redownloading multiple times. The window continues to block the way.