Categories and Month Archives no longer working

Hi there! I have been using this theme for a couple of years now and still love it. BUT, in the last couple of weeks, by categories seemed to have stopped working as well as my monthly archives.

So, in my sidebar, I have the categories and month archives. When I click on one of them, it just goes to a white screen. No specific errors are given, but nothing happens.

I tried deactivating all plugins with no change. Then, I changed the theme. The categories worked in the Twenty Fourteen Theme. So, it appears to be a theme issue.

Any ideas of what could be going on here? Is this theme still getting support from the author? I know the author was giving great support a couple of years ago! (Thanks!)