Unable to add a database to a subscription at Plesk > Subscriptions > Databases. The following error is shown:
There are no database servers available for this subscription
Not enough resources on the service plan.
Apply one of the following solutions:
Adjust Service Plan limits
Go to Service Plans > Example Plan > Resources tab where Example plan is the Service Plan name that subscription is assigned to.
Increase the number of the Databases or set any number different than "0" if this is currently set.
Click Update & Sync.
Note: solution affects all subscriptions assigned with the service plan in question and not locked.