I am working on a MacBook Pro mid 2014 that was bios locked. I bought a bios chip from bios depot on eBay and fed him the serial number and info and he made me a new bios chip. I replaced the one on the board and it worked fine for about a month then it failed and bricked the machine. I found a company in the Netherlands that make a small circuit board with the preprogramed bios chip on it. It plugs right into a port on the motherboard and it is awesome. It overrides the bios chip in favor of the new one and in minutes after getting it I am up and running. on eBay they have a few of the matts but if you look up there site they have many Mac models they support. I don't have the info in front of me but if you go to eBay and search for MacBook bios chip and "Matt" or
EFI BIOS firmware Matt Card Apple MacBook Pro 13" 2015
that will get you to one of there listing and get you in touch with the company. This turned my bricked MacBook back into a working machine in minutes. did take it a week or so to get here but it was worth it.
Hope this helps