This is interesting.
Could you run the "fltmc" command on this VM and see if the "vsepflt" driver is loaded ?
If it loaded and still eicar is not detected, uninstall the driver once and install it again and try once.
It cannot be a SVA problem because the VMware components is sending events to SVA. So if the vents does not even reach the SVA, how the scanning could happen. You can also see if this OS is compatible with the vSphere version being used.
Are you saying that only this Windows system has the problem where eicar is not getting detected.
Are these VM's in a cluster ?
Did it vMotion to diff vSphere ?
You can enable debug logs in SVA and see whether you are getting any events from this VM?
Been a while since I've used Agentless/vshield... But from memory in the vshield console it should show a list of VMs & there protected/unprotected status, do you see the expected info there?