Ok .. this is what you need to do:
* Drag & drop
* search again
* Click on "Installed" -> changes to "Update pending"
* Click on "Update pending" -> changes to "Update"
* Click on "Update" -> continues
The initial DnD operation simply opens the dialog, but doesn't do the search. So I guess it could be replaced by "Open MPC".
I don't want to blame anyone for this, but this is more than a bit confusing. Clicking three times on the same button is not what I would expect.
I guess the right resolution would be to wait for Oxygen.1a and hope that it will provide Java 9 support of the box. It is just two more weeks anyway.