ReasonCode type

The reason for the restriction. As of now this can be "QuotaId" or "NotAvailableForSubscription". Quota Id is set when the SKU has requiredQuotas parameter as the subscription does not belong to that quota. The "NotAvailableForSubscription" is related to capacity at DC.
KnownReasonCode can be used interchangeably with ReasonCode, this enum contains the known values that the service supports.

Known values supported by the service

QuotaId
NotAvailableForSubscription