Pinterest Pin It buttons stopped showing – images are large enough

Pinterest Pin It buttons were displaying and working on my website previously but they stopped showing on pages and posts about 2 updates back even though they are selected to show and there is a large enough image attached to a post or page. I am using:

WPSSO Pro Version 3.28.3
WPSSO SSB Version 2.2.1
Wordpress 4.4.2

Here is a link to an example post with the problem:

https://www.dynamicwingtsun.net/redbird-wing-tsun-new-kung-fu-club-isu/

I read the FAQ regarding similar issues and I have verified that the example post has a large enough image attached to the post (and included in the post). In fact, the image is 1600×2400. Here is a link to that image:

https://www.dynamicwingtsun.net/wp-content/uploads/hunter-watts-wooden-dummy-20160310_214427-1600×2400.jpg

I have verified that the srcset for the image in the source code includes an exactly correct resized image that is 800×1200. Here is a link to that resized image:

https://www.dynamicwingtsun.net/wp-content/uploads/hunter-watts-wooden-dummy-20160310_214427-1600×2400-800×1200.jpg

I have even made sure I explicitly specified the Image ID on the Select Media tab for the post to use the correct image and verified in the Head Tags tab that it says it should use this in the head tags:

meta property pinterest:image content https://www.dynamicwingtsun.net/wp-content/uploads/hunter-watts-wooden-dummy-20160310_214427-1600×2400-800×1200.jpg

I temporarily enabled Add Hidden Debug Messages and got this message:

WpssoSsbSharingPinterest :: get_html : exiting early: pin_use_img enabled but no photo available

The problem began approximately 2 updates ago. Strangely, on my dev site the Pinterest Pin It buttons show. The dev and production sites are on the same versions of everything, but the dev site is a couple posts behind and I updated the two sites separately rather than migrating from dev to production for these last updates.

I suspect that the problem occurred because I got the plugin update notice on the production site (a couple versions back) for the WPSSO SSB plugin before getting an update notice for the WPSSO Pro plugin. I updated the WPSSO SSB plugin and then got an error or warning that it required a newer version of the WPSSO Pro plugin. So I searched for updates to WPSSO Pro and found and installed the new update. But it was after having updated WPSSO SSB. And stupidly, I did that all first on the production site without thinking that I should do it on the dev site first. When I later updated the dev site, I did that in the correct order, first updating WPSSO Pro and then updating WPSSO SSB. The Pinterest Pin It buttons show on the dev site.

I even tried disabling, uninstalling and reinstalling WPSSO SSB on the production site and still have the same problem. Can you please help me fix this, hopefully without losing all of the work I put into customizing the WPSSO info for all posts and pages and all the likes and +1 counts? Thanks.

https://www.ads-software.com/plugins/wpsso-ssb/