[SOLVED]

error: failed to push some refs to ! [Rejected] main -> main (fetch first) (blaaa…..blaaa… blaaa)

in this case, you just use this command below to solve the problem

$ git pull origin master -allow-unrelated-histories

and then you can try again to push your code …..

$ git push -u origin master

I hope this article is useful, happy learning!