I clone my repository with:
git clone ssh://xxxxx/xx.git
But after I change some files and add and commit them,
Short answer: This error means the branch you want to push in remote doesn't exist!
In my case, starting from October-2020, the repos created since then had the main branch instead of the previous master branch. So all I had to do this:
git push -u origin main
Bingo! That worked for me! Hope that helps! Happy coding!