MacBook Pro High Sierra changing Standard user to Admin not working When I try to set another standard user (named "Owner") to an Administrator by clicking "Allow user to administer this computer", the box doesn't check, and instead I get a pop up window that reads "You must restart the computer for your changes to Owner's administrator settings to take effect."

All I can do is select OK and the box for making the standard user "Owner" an admin is still blank.

I've attempted to do this from both the Admin account, and the "Owner" account. Logged out of both users and also restarted the computer. None of these steps have made any difference.
I stumbled upon what I think is the answer.

I recently purchased this MacBook as a refurbished unit. The administrator user was sold to me without a password for access purposes.

Once I set up a password, all of the admin operations began to function normally.

I don't have confirmation that this is a particular security feature for Admin users without a password set up, but it seems to have solved the problem.