Since no one at Shareaholic has replied, I was forced to troubleshoot this myself. Here’s what I’ve figured out:
— Bitly: I realized after posting that I had updated Bitly’s DNS info on my custom link shortening domain per an email I received from Bitly advising they were upgrading servers. I don’t know if this caused the problem, and Bitly also never responded to an inquiry sent to them, so I may never know. If you’re having problems with any of the social media buttons you have activated in Shareaholic, I suggest trying the default Shareaholic link shortening service and seeing if sharing works.
— Featured Image: It was purely by accident that I realized the pages I was trying to share had no featured image (most of my pages do). If you don’t have one set, try setting one, and seeing if share to Google Plus works.
— Sidebar Comment: I now realize that setting an image in the Share section of Yoast isn’t picked up by Shareaholic. So it may be the Yoast plugin that’s my problem and not Shareaholic — it’s a chicken/egg thing; not sure if Y is causing S angst or the other way around.
Since I want both plugins and the featured image may or may not be set and I may or may not want the featured image to be the one shared, I’ve added this code to any pages/posts where I want to specify which image Google Plus picks up, and it’s worked for me so far:
<div class="none"><body itemscope itemtype="https://schema.org/Product">
<h1 itemprop="name">PAGE TITLE HERE</h1>
<img itemprop="image" src="IMAGE SOURCE URL HERE" />
<p itemprop="description">TEXT TO DISPLAY HERE</p>
</body></div>
Hope that’s helpful to someone.