Some POA-based resource was deleted from a subscription during Service Plan switch in PBA-E.
The Included value of the removed resource in the destination PBA-E Service Plan is set to 0 or there is no such resource at all in the Plan and corresponding Service Template in POA has included value set to 0 for the resource as well.
The general rules of resources handling during a Service Plan switch are described in the PBA-E Provider's Guide:
Resources included in both the old and in the new plans get their included value and upper and lower limits updated. Resources, included in the new plan but not in the old plan, are added with included value and upper and lower limits of the new plan. Resources, included in the old plan but not in the new plan, get their included value and upper and lower limits set to zero and respective services are disabled. No billing is done for the included resources. If the new plan supports resources, purchased under the old plan in addition to included resources, they are preserved under the new plan. Their quantities are kept and fees are updated. If the new plan does not support resources, purchased under the old plan in addition to included resources, their quantities are set to zero and respective services are disabled. Calculation of billable amount is made in the same way as for subscription fee.
So, if the destination Service Plan has the Included value set to 0 for some resource then PBA-E will set request to POA to set limit for the resource to 0. The same will happen if the destination Plan has no resource at all and the corresponding POA Service Template has the limit for the resource set to 0 as well (or does not have the resource included at all).
Keep in mind that resources may be physically destroyed (unprovisioned) in the customer's subscription which may lead to unrecoverable data loss.
The customer has to purchase additional units of the resource in their subscription after the Service Plan switch. If necessary, they need to recreate hosting objects in Control Panel as well.
To avoid such issue in the future Provider has to correct resource limits in their Service Plans, e.g. set included limit for resource to non-zero value.
Also resource mapping can be configured for equal resources.