hi,
Sync Client will connect to pydio via api with this uri. Try some request (with browser) on following uri:
/api/workspace-slug(id)/ls
/api/workspace-slug(or id)/changes
if it does not work, make sure you have correct version of .htaccess (example: https://github.com/pydio/pydio-core/blob/develop/core/src/.htaccess)