I had this problem suddenly after an update (update released yesterday) because i didn't have it before. Checking it, i saw that my user was in the admin group, but no in the sudo group, so after adding the user to the group, i have the button again.
I had this problem suddenly after an update (update released yesterday) because i didn't have it before. Checking it, i saw that my user was in the admin group, but no in the sudo group, so after adding the user to the group, i have the button again.