Multiple VM's seem to be regarded as the same VM by webroot

I have a problem with several VM's that I am adding webroot to – it only seems to recognise them one at a time, i.e I add VM2 and the VM1 vanished from the endpoint list. Restart VM1 and it reappears, only for VM2 to vanish.
 
 
I suspect this is related to them both being clones from a template (call it VM0). I ran SysPrep on VM0, then cloned it 4 times, entering new registration and computer names for each clone. Maybe I should have run SysPrep again on each clone.
 
 
Or maybe it is because they are all licensed under the same MAK (Multiple Activation Key).
 
 
What does webroot use to uniquely identify a PC? Hopefully there is a procedure for me to generate a new ID for the VM's if this is the problem.
 
Thanks - Lindsay