Git failed to push some refs to remote:
I faced this issue mostly if I have cloned one repo and trying to commit something. The main reason of this error is that your branch is not in sync with the remote. This problem mostly occurs if you are working on the same branch of the repo with other persons in a team.
How to fix this:
As I said before, the main reason of this issue is that your local changes are not in sync with remote. The easiest way to fix this is by taking a pull and merge the changes with local changes. So, use a git pull.
git pull --rebase origin master
then, push the changes.
git push origin master
If you are working on a different branch, not on master, you can use that branch name. This should fix this issue.