When re-deploying an already deployed system with ConfigMgr 2012, an error message is sometimes displayed: "Failed to Run task sequence, There are no task sequences available for this computer". This because the system is already available in the ConfigMgr console as a "unknown" system. Because of that the "All Unknown Computers" deployment isn't used and a deployment on a known computers collection isn't used also. This because in system properties: "Unknown Computer = 1" is detected. No way to install this system again!?
As a workaround it's possible to delete the created object in ConfigMgr collections to re-deploy a system again. After deleting the system(s) the error message: "Failed to Run task sequence, There are no task sequences available for this computer" will be gone. Unfortunately after re-deployment the same thing happens again, so it's no real solution to this problem. Another solution to resolve this is mentioned HERE. It says: Add a query rule to the Collection that grabs new computers where the System Resource “Unknown Computer” property = “1”.
I tried that solution myself also, but it don't seems to work either. A "Unknown Computer Bug Update" can be found HERE. It mentions:
"The final response back from Microsoft via Connect was that this would be submitted to the Product Group as a Design Change Request". Hope it will be solved soon! Strange enough I don't have this issue at all ConfigMgr 2012 implementations? Anyone?
Update: For it seems this is only a problem when working with workgroup systems. When working with domain members there isn't any error message. That explaines why I haven't see this problem before.
Update 16-6: Unchecking "Unknown Computer Support" on the DP/PXE in question restarting the executive on the Primary and then reselecting "Unknown Computer Support" on the DP/PXE in question and restarting the executive resolves this issue. The problem you're running into is an corrupt policy on the MP. By Unchecking the option mentioned this will create a new policy and your unknown systems should pick up the TS when in WinPE.