Get three columns in the footer

Apologies that I can’t help but this is something I am also trying to do (and have spent dozens of hours trying to achieve).
None of the ‘usual’ bits of code seem to work.
I can register the extra widget area (or register a whole new set of three) but then only one ever actually appears on the live site. It’s all code I’ve used before successfully so I’m assuming there’s some conflict in this theme. Struggling to find it though.