Yes, as @unagi_pie suggests, you will need to write a commit message otherwise the sync will fail. You should see an error in your console (if Coder is open), such as
File "C:\Users\lpzdb\psychopy\psychopy\app\builder\builder.py", line 2379, in onPavloviaSync
pavlovia_ui.syncProject(parent=self, project=self.project)
File "C:\Users\lpzdb\psychopy\psychopy\app\pavlovia_ui\project.py", line 477, in syncProject
outcome = showCommitDialog(parent, project)
File "C:\Users\lpzdb\psychopy\psychopy\app\pavlovia_ui\functions.py", line 150, in showCommitDialog
project.commit(commitMsg)
File "C:\Users\lpzdb\psychopy\psychopy\projects\pavlovia.py", line 950, in commit
self.repo.git.commit('-m', message)
File "C:\Program Files (x86)\Python36\lib\site-packages\git\cmd.py", line 548, in <lambda>
return lambda *args, **kwargs: self._call_process(name, *args, **kwargs)
File "C:\Program Files (x86)\Python36\lib\site-packages\git\cmd.py", line 1014, in _call_process
return self.execute(call, **exec_kwargs)
File "C:\Program Files (x86)\Python36\lib\site-packages\git\cmd.py", line 825, in execute
raise GitCommandError(command, status, stderr_value, stdout_value)
git.exc.GitCommandError: Cmd('git') failed due to: exit code(1)
cmdline: git commit -m
stderr: 'Aborting commit due to empty commit message.'```