Unable to increase disk size of Windows Virtual Machine

've been trying to increase the disk size of my Windows 10 VM. It's currently set at 128GB, however when following the instructions of deleting all snapshots before being able to do this, I keep getting the warning "Unable to edit the hard disk properties because it has one or more snapshots." I click Manage Sanpshots and there are no snapshots!

Given the above, how do I change the size of the virtual disk so Windows?