No Paragraph Breaks

I used WP for a while, with Visual Editor on, and no problems. I’ve recently noticed, my last couple of posts stopped recognizing the paragraph breaks. So I turned the theme back to WP Default, and deactivated all plugins. This did not solve the issue.

Searching the forum, I took advice to turn off the visual editor, used <br> in the post. This worked.

However, clients aren’t impressed they can’t just hit RETURN and use the other Visual Editor features. They don’t want to code. Any ideas on what could be causing this problem, how to fix it?

If there is a change to be made in the Wp install code in any advice given, please be very specific about where to change that code.