You’ve extended a virtual disk in Vmware or Proxmox for a Windows virtual machine, but the disk appears the same size in Disk Management?
Try shrinking the disk a bit—for example, by as few as 2 megabytes. In my case that’s what helped Disk Management suddenly discover new unallocated gigabytes, which I could use to expand the filesystem.
Remember to have a proper backup and do this at your own risk.