Why can't I install anything? No error given, just endlessly "tries"
It's been happening again lately, but 2 or 3 times now it's resolved itself when I cancelled another forever-pending update I never requested. I get the feeling it's like 2 or more updates are stuck in the door, and neither wants to let the other go first.

Whatever's going on, and in lieu of another, better answer, try this - go to Google Play, tap for the menu (the "hamburger" in the search field) and click "My apps &amp; games." X off updates till one starts making some progress.