your branch is behind origin/xxxx

Your branch is behind 'origin/main' by 20 commits, and can be fast-forwarded.
 (use "git pull" to update your local branch)

Solution: git pull

git fetch origin
Your branch is up to date with
Error: unable to reach remote default branch

See also

• git pull [ -v | -a ] git request-pull, git pull origin master Pull Request (PR), --no-rebase, --rebase
• git status, git diff, git add, git restore