I clone my repository with:

git clone ssh://xxxxx/xx.git 

But after I change some files and add and commit them, I want to push them to the server:

git add xxx.php
git commit -m "TEST"
git push origin master

But the error I get back is:

error: src refspec master does not match any.  
error: failed to push some refs to 'ssh://xxxxx.com/project.git'

Maybe you just need to commit. I ran into this when I did:

mkdir repo && cd repo
git init
git remote add origin /path/to/origin.git
git add .

Oops! Never committed!

git push -u origin master
error: src refspec master does not match any.

All I had to do was:

git commit -m "initial commit"
git push origin main

Success!