With this error message Gerrit rejects to push a commit if the pushed commit was already successfully pushed to Gerrit in project scope. In this case there is no new change and consequently there is nothing for Gerrit to do.
If your push is failing with this error message, you normally don’t have to do anything since the commit was already successfully pushed. Still this error message may sometimes come as a surprise if you expected a new commit to be pushed. In this case you should verify that:
your changes were successfully committed locally (otherwise there is no new commit which can be pushed)
you are pushing the correct commit (e.g. if you are pushing HEAD make sure you have locally checked out the correct branch)
If you are sure you are pushing the correct commit and you are still getting the "no new changes" error unexpectedly you can take the commit ID and search for the corresponding change in Gerrit. To do this simply paste the commit ID in the Gerrit Web UI into the search field. Details about how to search in Gerrit are explained here.
Please note that generally it only makes sense for each commit to be pushed only once. This means:
you cannot push a commit again even if the change for which the commit was pushed before was abandoned (but you may restore the abandoned change)
you cannot reset a change to an old patch set by pushing the old commit for this change again
if a commit was pushed to one branch you cannot push this commit to another branch in project scope (see exception).
if a commit was pushed directly to a branch (without going through code review) you cannot push this commit once again for code review (please note that in this case searching by the commit ID in the Gerrit Web UI will not find any change), see exception.
If you need to re-push a commit you may rewrite this commit by amending it or doing an interactive git rebase, or see exception. By rewriting the commit you actually create a new commit (with a new commit ID in project scope) which can then be pushed to Gerrit.
If you are pushing the new change to the same destination branch as the old commit (case 1 above), you also need to replace it with a new Change-Id, otherwise the push will fail with another error message.
Sometimes a change no longer makes sense to be destined for a specific branch, and instead of trying to re-push the commit for a different branch, it makes more sense to move the change to the preferred branch (where it will now likely need a rebase). Moving the change instead of pushing a rebased commit to the preferred branch helps to retain code review comments and any previous patchsets on the original change.
You will also encounter this error if you did a Fast-forward merge and try to push the result. A workaround is to use the Selecting Merge Base feature or enable the Use target branch when determining new changes to open configuration.
Part of Gerrit Error Messages