Proxmox VE is based on Debian but is using current Ubuntu kernels to have better support for current hardware and access to new features. This means that if you ask vendors about compatibility, it is more accurate to ask about their Ubuntu support. Currently, Proxmox VE is using version...
Have you a subscription  valid?
If you don't have a subscription make sure to use the non-subscription  in the PVE repository.
There are no errors during balloon installation?
what error did you get?
Which version of VirtIO are you using? did you checked our wiki  and 
May you post or send a screenshot of the error you got during the installation?
what kind you hardware that you trying to install PVE on it? However, you still can install Proxmox VE on top of Debian Buster 
are the Balloon and QEMU running inside the Windows VM?
Please post the VM config and the output of the following commands:
From Proxmox VE side:
From Windows 10 VM:
sc qc BalloonService
sc qc QEMU-GA