Synapse Workspace does not have managed virtual network enabled by default.
When you create your Azure Synapse workspace, you can choose to associate it to a Microsoft Azure Virtual Network. The Virtual Network associated with your workspace is managed by Azure Synapse. This Virtual Network is called a Managed workspace Virtual Network.
Managed private endpoints are private endpoints created in a Managed Virtual Network associated with your Azure Synapse workspace. Managed private endpoints establish a private link to Azure resources. You can only use private links in a workspace that has a Managed workspace Virtual Network.
Your Synapse workspace is not using the private endpoints
Set manage virtual network to enabled
The following example will fail the azure-synapse-virtual-network-enabled check.
The following example will pass the azure-synapse-virtual-network-enabled check.