With this error message Gerrit rejects to push a commit for code review if the pushed commit and the commit at the tip of the target branch do not have a common ancestry.
This means that your local development history and the development history of the branch to which the push is done are completely independent (they have completely independent commit graphs).
This error usually occurs if you do a change in one project and then you accidentally push the commit to another project for code review. To fix the problem you should check your push specification and verify that you are pushing the commit to the correct project.
Part of Gerrit Error Messages