Google Deploy to App Engine disabled in Eclipse

Question

I am using the Google Plugin for Eclipse to deploy my project to App Engine, and this has worked great for over a year. But a couple of days ago it stopped working, and I can not seem to find the reason. The project is still an App Engine project, but the Deploy to App Engine button is disabled.

I already reinstalled the entire Google Plugin in Eclipse. I also added another GAE project, but then the button is still disabled. I managed to enable the button once to upload, but I don't know what triggered the enabling.

Has anyone seen this before and any clue on how to fix this?

EDIT: The button enabled when I removed and re-added the App Engine SDK from the build path of the project. After the deployment, the button disabled again..

Answer 1

This is a known bug in the latest 3.9.1 release. The fix will be pushed on Monday, 5/2.

Answer 2

The same thing is happening for my eclipse mars. The workaround I'm using is, File >> Close Project, then double click to open project, voila.