There are some prerequisites for VHD Disks that need to be ready before decide to present VHD Disk in WAP to be used why Virtual Machine Provisioning that will save you a lot of troubleshooting time if you verify all as follows:

  1. Library Share that hosts the VHD must be added to the list of Read-Only shares in Cloud Properties in VMM.
  2. The VHD must have “FamilyName” property configured.
  3. The VHD must have “release” property set in the format like n.n.n.n (e.g. 1.0.0.0).
  4. The VHD must have the Operating System property set.
  5. VHD must have the required Tags by Gallery item, the Tags requirements can be found in Gallery item’s readme, this property can be configured only through VMM PowerShell using set-scvirtualharddisk cmdlets, knowing that Data VHD Disk does not require Tag.

More resources with more details for each step that include videos as well can be found here:

Troubleshoot Gallery Item:

http://blogs.technet.com/b/privatecloud/archive/2013/11/27/troubleshooting-windows-azure-pack-and-gallery-items-part-2.aspx

Troubleshoot WAP:

http://blogs.technet.com/b/privatecloud/archive/2013/11/08/troubleshooting-windows-azure-pack-spf-amp-vmm.aspx

Troubleshoot SPF:

http://blogs.technet.com/b/scvmm/archive/2013/11/12/general-troubleshooting-list-for-windows-azure-pack-wap-and-spf-integration.aspx

As a conclusion, you should be aware about all the above prerequisites that need to be verified before start testing creating VM using VHD Disk or from Gallery.