I have both the latest Flash plugins installed, the plain Adobe, and the PPapi? (not sure I spelt that correctly), but install manager keeps launching, and prompting me to update. This happened before, maybe 2-3 months ago, and seemed to resolve itself.
I have always used the official install manager.
|YOUR SYSTEM INFORMATION|
|Your Flash Version|
|Your browser name|
|Your Operating System (OS)|
It might be that one of the Flash Player is updated and the second one is not. This could be the reason that you are seeing update notification. Could you go to system preferences-> Flash Player -> Updates tab and take a screenshot and share the same.
Flash uninstalled from my computer.
Stalle Help Flash player