Tasks to provision Windows-based services fail in POA with error message '0x800706b5: The interface is unknown' like in the example below:
Task name Create virtual web server 101 (domain_id=1, hd_id=100101) on host 'winweb01.hosting.local' (host_id=53). Method name taskCreateWebSite on OBJREF:iis:0:getDomainService:41329 Last execution output Destination host_id #53 : Provisioning request failed. The interface is unknown. [<response><errorContext description="Could not open metabase key. IIS://winweb01.hosting.local/W3SVC/AppPools 0x800706b5: The interface is unknown." code="0x800706b5" executeSeqNo="20"><errorSource namespace="Error Provider" procedure="SetError"/><errorSource namespace="Error Provider Ex" procedure="RethrowError"/></errorContext></response>]
Usually the reason of the problem is lost connectivity between MPS (Microsoft Provisioning Service) server and target hosting server, IIS server winweb01.hosting.local in the example above. It may happen due to network connectivity issues or stopped/hanged MPS or hosting service.
Check if the needed service is up and running on the destination shared hosting server - IIS in the case above, ID of the server may be found in the failed task properties.
Check the basic connectivity between MPS server and shared hosting server using e.g. ping.
Restart MPS engine using instruction in the Knowlwdgebase article #1851 How to restart MPS Provisioning Engine properly.