Cant change mac address??

ok guys im a noob but it used to be as easy as setting up TMAC clicking a button and boom my mac address is changed. NOW i get an error message everytime, i change the beginning to 02 as it says and still doesnt work. i tried to do it the manual way through device manager… checked command prompts and still the address that shows up isnt the original mac address that shows OR the one i changed it to. help is appreciated, thanks.