The project description file (.project) for my project is missing

I've found this solution by googling. I have just had this problem and it solved it.

My mistake was to put a project in other location out of the workspace, and share this workspace between several computers, where the paths difer. I learned that, when a project is out of workspace, its location is saved in workspace/.metadata/.plugins/org.eclipse.core.resources/.projects/PROJECTNAME/.location

Deleting .location and reimporting the project into workspace solved the issue. Hope this helps.

I had the same problem and in my case .project file was also present in the project directory and had correct permissions.

This problem happened to me after I closed and reopened multiple projects quickly one after another and Eclipse tried to rebuild them at the same time.

In my case Eclipse lost .location file in the workspace directory for 2 out of 5 projects: <workspace>/.metadata/.plugins/org.eclipse.core.resources/.projects/<project name>/.location

I've followed instructions on How to get project list if delete .metadata accidentally and imported the project in the workspace manually via File :: Import :: Other :: General :: Existing Projects. After that .location file was created again and Eclipse stopped complaining.