User blog comment:Rappy 4187/Technical Update: December 9, 2015/@comment-1430834-20151230143610/@comment-957747-20151231180524

That's due to the fact that the most recent changes are ones that are not shown on WikiActivity. As seen here: http://toarumajutsunoindex.wikia.com/wiki/Special:RecentChanges there were a lot of file page changes done recently. Unfortunately, this blanks the WikiActivity because no relevant changes can be shown there.