Thanks for your response, Shanon.
Different senders. Rebuilt Inbox. The three options in the Privacy pane are off. My work-around is to Forward the message and the content is shown in the Forwarded message window. Problem happens intermittently from commercial and personal senders. Sometimes a Restart will fix it. The content shows if I go to Mail on the iCloud website.
Unfortunately, this is one of the several problems I'm having with Monterey, like intermittent denial of permission to save a file. Resetting permissions for the folder fixes it for awhile. Thanks again.