my scenario is when everything working properly and yet you never see your new items/pages in your variations targets.
this is actually an embarrassing thread, but i'll write it for the key searches I've made without any results.
the reason might be you just misread, or never read, the variations docs to the end, well i guess its there since i never really read them either.
anyway if you set the target variation to be updated automatically it will only take Published items, so make sure you publish you content where needed.
but if you set it to be manually updated then the Ribbon Button "update all variants" is initially grayed out.
you must select items and only then push it.
its a bit tricky since:
a. if you want to copy entire list/lib you need to select them all, sometimes its a lot.
b. if you select a sub-folder it doesn't work.
the solution to the above will be to create a designated view (flat view - no sub-folders).
p.s. from a certain amount of items it will be impossible, since the view cant be calculated (can be changed in central admin).