I have a site and within the root I have a folder called years, within those I have folders for 2013/2014/2015. Each of those folders contain whole sites. On the main index.html I have links under archives pointing to index.html within those folders but when I click on them I get an WordPress a Oops! That page cannot be found error. Can I not add sub-sites in this fashion?
are you using 2013/2014/2015 as sub-folder in a Muse site that you uploaded in the mtw-themes (you can’t, create 4 folder)
2013/2014/2015 is a the root of your WordPress maybe try to use the complete path to the page (including the site http, domain …)