Power locks don't work

[D-YukonXL]

I saw on another forum where pressing the unluck button twice turns auto lock on. The fix was pressing unlock once then pressing it again and holding it for 5 seconds tried this yet?

In order to change the lock mode you must press twice quickly. This is in service mode of course. I havent held it for 5 seconds tho.. I will try that one. Thank you!