The error 'fatal: ref HEAD is not a symbolic ref' means that Git has lost the symbolic reference from HEAD, which points to the active branch in a standard setup. Typically, this error arises when cloning or using a repository in a detached HEAD state, meaning HEAD is pointing directly at a commit instead of a branch. To resolve this, switch back to a valid branch using `git checkout main` (or the primary branch name in your repo) to reset the symbolic link of HEAD. If the branch doesn’t exist, use `git branch -a` to list all branches and create or switch to the appropriate one. Additionally, inspect the .git/HEAD file to ensure it points correctly to your branch by containing something like `ref: refs/heads/main`. Restoring HEAD to a symbolic ref fixes this issue, allowing Git to reference branches correctly moving forward.