All newly created subscriptions or already existing ones assigned to this service plan become unsynced with the following message in Plesk interface:
Syncing the subscription with its service plan failed because some of the services or resources defined in the plan cannot be actually provisioned with the subscription.
Warning: Could not sync the subscription with the service plan. The following settings of the subscription conflict with the service plan: Hard disk quota
The Hard quota on disk space is not available for editing at the Plesk > Domains > example.com > Web Hosting Access page:
Unlimited. Hard disk quota is not supported due to the configuration of the server file system
Behavior, when the Hard disk quota value is manageable at the Plesk > Service Plans > Default > Hosting Parameters page, while Hard disk quota is not configured on the server itself, is considered as a Plesk bug #PPPM-9163 which will be fixed in future updates.
Until the fix will be available the following workaround is applicable:
Go to the Plesk > Service Plans > Default > Hosting parameters page.
Mark the Unlimited checkbox opposite the Hard disk quota directive.
Press the Update & Sync button.
Note: Changes will not be applied to the locked subscriptions.