If you have not specified inventory mappings for your site, you must configure resource mappings for individual virtual machines. You can configure resource mappings only if site-wide inventory mappings have not been established.
If inventory mappings have been established for a site, you cannot override them by configuring the protection of individual virtual machines. If you need to override inventory mappings for a few members of a protection group, use the vSphere Client to connect to the recovery site and edit the settings of the placeholders or move them to a different folder or resource pool.