Issue:
You have just added a new VPP application and trying to set “Force license association to device” to ON. However the Option is grayed out.
Solution:
XenMobile needs to complete the VPP license sync, you need to wait for this to complete before the setting can be adjusted.
If you have just added a new VPP account which has a lot of applications added to it the license sync may take a long time to complete.
Note: The application also may not be enabled by the developer for VPP device based license assignment.