Unable to re-install one app

[Easttime]

A few weeks ago, iOS app store was funky. I would click "Update All" for a number of apps needing updating, and they would simply switch to "Update" but nothing would happen. That passed. But one of the apps (Dropbox, probably not significant which app) remained stuck. So I deleted it from my iPad, searched for it on App Store, and found that it has the round-circle-dot-in-the-centre icon instead of a download icon. Nothing happens when I click on it. I tried signing out and back in via settings, and rebooting the iPad, and leaving it three weeks, but still the same. All other App Store updating functions are working fine for all other apps. Any suggestions? Thank you.