For cannot find VM issue, I will suggest to check the VM name(VADP_VM_NAME) specified in the client resource. Make sure this one is the inventory name in vSphere, not the computer name, and it is case-sensitive.
For the VMs not synced in Virtualization, yes, this issue sometimes exists. You may try to re-run the auto-discovery. If the issue still persists, I will suggest to upgrade to version 8.x, as 7.6.4 version is out of our service life now.