Provider configured Parallels Key Administrator plug-in in PBA to sell licenses to customers.
In plug-in configuration Provider enabled the option Downgrade is allowed at
PBA Top > External Systems Director > License Manager > License Management Plug-ins > KA plug-in.
However, customer cannot downgrade their license in PA Control Panel. E.g. customer purchased Parallels Plesk Panel license with 300 domains and they cannot downgrade license to 10 or 100 domains.
Downgrades are not supported for resources of 'license' type. Downgrade is allowed checkbox is reserved for future functionality.
To change a license to a lower capacity, an existing license should be terminated and then a license of a lower capacity can be ordered.