If your installation didin’t create a default admin user, you may have more problems that this. However...
Check user_roles, if there isn’t one make one:
INSERT INTO `modx_user_roles` VALUES (1, 'Administrator', 'Site administrators have full access to all functions', 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1);
You also need an entry in user_settings to establish your user’s role and other settings:
INSERT INTO `modx_user_attributes` VALUES (1, 1, 'Default admin account', 1, '[email protected]', '', '', 0, 0, 0, 0, 0, 0, 0, '', 0, 0, '', '', '', '', '', '');