A badge or indicator should be present on apps already installed. Perhaps with status "Current" or "Upgrade Available"  

Agreed, an upgrade was available for one of my apps and I could not upgrade because the system stated it was current, which it wasn't obviously.

44 minutes ago, Davyc said:

Agreed, an upgrade was available for one of my apps and I could not upgrade because the system stated it was current, which it wasn't obviously.

That doesn't sound right, there should be an upgrade button if there is an upgrade available. If your AdminCP is still in that state where the issue is visible, please submit a ticket.

25 minutes ago, Stuart Silvester said:

That doesn't sound right, there should be an upgrade button if there is an upgrade available. If your AdminCP is still in that state where the issue is visible, please submit a ticket.

I will if it happens again - I had to delete the app and then install the newer version, so it's all good now; it was fortunate that the app was not essential so no data was lost 🙂