Message button missing from Photos, et.al.

Hi:

I've got a 6S (MKQA2LL/A) (unlocked) on Verizon. Upgraded to iOS 11 and so far have only noticed one problem: my "Message" button is missing from the Photos app.

When I select a photo to share, then I tap on the box with the upward arrow pointing outward (lower-left corner of screen). This typically brings up the option to share by Message, Mail, Notes, iCloud Photo Sharing, etc -- between the AirDrop area and the Copy/Duplicate/Slideshow/etc. buttons. The Message "button" is missing from this "sharing page" when loaded by other apps, too (Safari, Maps, etc.).

Is there some setting that I'm missing? Other apps withEverything else seems to work OK.

thanks!