It's certainly possible that they might not have a block diagram. That is an option when saving VIs and often third-party vendors will distribute VIs that way as a security measure. When creating an LLB meant for an executable, the diagram will be removed as well. Where did the VIs come from? Can you attach one of them? If they truly have no block diagram, then there is nothing that can be done. Once deleted, the block diagram is gone forever and without a block diagram, a VI cannot be recompiled for a newer version of LabVIEW.
