shortcode gallery not showing all images

I have a page w/ 16 images attached in the gallery, but only the first 8 are showing up on the page. any thoughts?? Not the first time I’ve had this problem and it’s not always 8. thanks.

paying more attention, I realize it seem to be the first 1/2 of the attached images are displayed and the rest are not. ie, if I attach 14 images only 7 are displayed on the page. 12 and only 6 are displayed.

??