Hi everybody,
I have a solution here. I've been trying to get his done ever since I bought my used 2016 model S 60D about 6 months ago, and finally got it done yesterday (11/19/2020). I spoke with a gentlemen at the Tesla service center in Clarkston, Michigan name Ricky. He was very helpful. His email is "Rbayne at tesla dot com" (I purposely typed the email like that so his email address does't get picked up by spam bots) or you can just call the Tesla service center in Clarkston MI (248) 241-9321 and ask for Ricky.
He said there is an issue with the apps and online accounts where the option no longer shows up there and that has caused many who work at Tesla to assume that it is no longer offered. But it is. I had to make an appointment and bring my car there, but they were able to do it. It cost about $2,400 with tax on my model S.
If you're within driving distance of Clarkston, MI, you could just go see Ricky. But if not, still get in touch with him and see if he can help facilitate the upgrade with your local service center.