One of my sites is broken today

I've noticed 2 huge problems with one of my sites today. We have published 8 or so posts on since May 22nd but none of those are appearing on our homepage. Only the ones from May 22nd back. The homepage is set up to display latest posts so they should all be there.

Also all of the drop-down categories are displaying "It seems we can’t find what you’re looking for. Perhaps searching can help." messages where before there was content in each of them. I suspect the 2 issues are related but I've been unable to find anything that might be wrong.

I've granted support access and I would be grateful if someone could take a look and see if you can tell what's going on.