There could be faulty include path in config.core.php
You will need to update the db settings and local paths in these files:
public_html/config.core.php
public_html/core/config/config.omc.php
public_html/core/cache/system_settings/config.cache.php
This seems to be what is needed to get MODx to work (if one has defined it with absolute paths to folders etc)