I've got a Genie Powerlift 900, and every time I've tried to program a new car with it, neither the Homelink's instructions, nor the car's instructions worked. The same was true for my '17 Explorer while I tried every recommended set of instructions this weekend.
The good news is that on each of these occasions, I called Genie support and they walked me through a completely different and undocumented set of instructions that worked each time. They were closed this weekend, but I will call them later this week to sort out the Explorer.
I'm not sure if Chamberlain offers the same level of support as Genie, but I would give that a try. Good luck.