こちらを読んで解決しました
以下のようにgerritへのgit review時に"no new changes"と出てpushできない場合、

$ git review
...
xxx(no new changes)
...

かつ、以下にも該当しない場合、

1.your changes were successfully committed locally (otherwise there is no new commit which can be pushed)
2.you are pushing the correct commit (e.g. if you are pushing HEAD make sure you have locally checked out the correct branch)

既存のcommit IDと重複している可能性がある。

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.

git commit --amendでcommit IDを更新すれば解決するかもしれない

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.

参考

https://gerrit-review.googlesource.com/Documentation/error-no-new-changes.html