Why can't Pinterest fetch images from sites with SNI based SSLs?

So, last year, Google said that SSLs are now a ranking signal.

Joost de Valk expounds on why you need SSLs (security, proof of seriousness, future proofing, etc.).

So, we switch all domains to Comodo SSLs.

Then, the barrage of visitor complaints begin because they can suddenly no longer Pin from our sites to Pinterest.

Sure enough, despite hundreds of thousands of prior Pins, the same site with SSL can no longer Pin to Pinterest and all attempts result in a, "We couldn't fetch the image" error.

I'm running AWS EC2 instances with a standalone RDS database server.

Pinterest also runs on AWS EC2 instances.

Pinterest also runs SSL.

So, why can't my website visitors Pin to Pinterest?

As a temporary workaround, we've re-routed the domain at Wendy Polisi to use an alias with an AWS Elastic Load Balancer which fools the Pinterest script into allowing the image to be fetched and the Pin to be registered, but this has been fraught with its own debacles. There have been 3 node failures in the last week alone causing the site to display chronic intermittent WSOD and requiring us to notify AWS so they can replace the node so we're going to eliminate this as a "solution".

Why can't Pinterest, who's on AWS also, who's running SSL also, fetch the image natively?