This error often occurs after another checkin has gone in before yours, and says “the tip of your current branch is behind its remote counterpart”.
It should be resolved by
a) ‘git pull –rebase’ // this may bring in conflicts that need to be resolved
b) ‘git push’ // this works the first time
After the two steps your changes are available to team members to code review and you may need to edit your changes. After making such changes, you’d need to do
c) ‘git push -f’
to force the push.
However say this codereview-edit cycle takes some time and other changes are approved in the mean time – then you have to repeat these steps.
It can be simpler to get a fresh copy of the top of tree and add in your changes directly there and submit.