feed suddenly not working

Suddenly, actually in the last couple of days, my feed quit working. My sister brought a feed to my blog into hers and it worked. She just removed it and wanted to subscribe in Google reader, and couldn’t. When I checked I get a message that the feed doesn’t exist.

my site is https://otlewski.net

my feed url shows as: https://otlewski.net/feed/

I haven’t touched any files so can’t imagine why this isn’t working. I recently changed my theme, but it had been working up until now with the new theme. I tried changing back to my old theme, but still no luck.

Any ideas?