Can't enable periodic assessment in Update management center

Hi,

I am trying to test out Azure update management center as a way of managing our VM OS updates instead of continuing to use our current third-party tool. However, every time I try to add a VM to enable periodic assessment for updates, I get an error;

"The selected VM(s) image is not supported for changing "Update Settings" because the VM is created from https://learn.microsoft.com/azure/virtual-machines/linux/imaging?WT.mc_id=Portal-fx#specialized-images."

However, none of our VMs are created from a specialized image, they've all been manually configured from the offered Windows Server 2019 Datacenter Edition image offered when manually creating a regular (non-Arc) x64 Gen2 VM from scratch in the Azure portal. All are hosted in Canada Central.

Manually checking for updates on a given VM from the portal works, but this is pretty useless, and we need the ability to check and apply updates on a schedule.