I realise that it's been some time since your original post and perhaps you've found another way around this, but the fact remains that this is still happening as I, myself have experienced this problem today in January 2021.
Some people have reported that reinstalling windows fixes this and some appear to have just uninstalled and reinstalled "Samsung Magician" to get it to work...?
My solution to this problem was to disable my Windows 10 Home data security software and then just rerun the Over Provisioning process.
The data security software that I disabled/shut down was "Norton 360 Autoprotect" and "IBM Trusteer Rapport" I'm not sure which one of these it was that was causing the problem but suspect it was "Norton" as it does protect against other programs accessing the disk drives at a low level which the "Samsung Magician" utility is obviously going to be attempting.
Since most antivirus/malware etc protection software will be working in a similar way to "Norton" I would suggest anyone else with this problem try disabling their antivirus software in the first instance an then trying to set the "Over Provision"
If it works for your report back here with a comment regards the software you had to disable so that this can seen by others and the problem can be marked as solved.
SAMSUNG: (if you're listening...?) If this is a solution it might be worth you advising people, via a message in the Magician utility, to disable antivirus software etc before trying to set the OP.
