page w/query slug not displaying posts

Greetings. I’m running WP 4.2.2 on 64-bit Ubuntu LTS 14.04. The site has been up and running for a couple of years, and there have been no structural changes in several months.

I’m having a problem that a static page that contains only:

[query slug=”newsletter”]

and with no other customizations (no parent, default template) has suddenly stopped displaying newsletters (text and associated links). We have one newsletter a month, and I’ve been pushing them to the web site w/o problems until yesterday.

There certainly *are* posts with the “newsletter” category, and the slug for that category is “newsletter”.

I might add that we have a “podcasts” page with the exact same structure (no customizations) and content consisting only of:

[query slug=”podcasts”]

This page is still working fine, which suggests to me that the underlying “machinery” is intact.

If you have any thoughts about this, please pass them along to me. Thanks.

— Mike