You can't change your MAC address on new Macs
Jul 13, 2019
Yay! This was fixed in the release of macOS Catalina.
Replace the MAC address in the following command to whatever you want and it should work.
$ sudo ifconfig en0 ether 00:80:48:ba:d1:30
For almost a year the ability to change the MAC address on MacBooks has been broken or disabled.