Gary, yeah it’s a puzzle to me as why it doesn’t work on the mobile version.
Thinking about it, I am using version 15 to generate the website, could that be the problem ?
It shouldn't be. And I created several sites with mobile variants in several previous versions without any problem.

Is it possible for you to upload a singe page with the variant page?

Another thing, can you create a single new page and a variant and publish just to see if those upload and work in the mobile version. Sometimes a page gets corrupted for who knows what reason and this might be a cause.