Hyper-V - available virtual desktops not showing anything

Hi,

We are testing a Windows Server 2016 Hyper-V server environment of three servers with ten Windows 10 VDI's running on it (personal unmanaged) and we have a collection with those virtual machines in it.

We created a new virtual machine and it's running fine on the VM Host server.

But when we want to add a new virtual machine to the virtual desktop collection it is not showing, so it cannot be added to the collection.

We have to reboot the VM Host server before the new virtual machine will be visible.

How can this new machine be seen and added to the collection without the need to reboot the VM Host server (where other VM's are running on)? 

Thanks,