How to shrink Windows 10 partition when shrink size is 0

I have more than 500GB free on my C: drive but Windows Disk management says that the shrink size is 0. I followed all the steps here, here, here and here but none of these solutions worked:

• Turn off Virtual memory
• Turn off System Restore and delete restore points
• Turn off hibernation
• Disable kernel memory dump

After having done all these, the shrink size remains 0.