pinterest share button no longer generating its own image

Hi! I found similar help topics but didn’t come across any quite like this. I apologize if this is redundant or misplaced.

A short time ago (I last recall being able to do it in February, haven’t necessarily tried since) I was able to click the Pinterest share button in pages on my site and it would generate its own thumbnail if there were no images available. Like this:

(I tried pasting screenshots but it wouldn’t let me?)

I tried to do that again today, just wanting to share the fact that the page exists with my followers, but no image appeared on the Choose Board pop-up, and when I tried to save it (just to see if it would) I got this error message: Something went wrong – You need to upload an image or provide the ‘image_url’ parameter.

I suppose it could be a Pinterest issue, though it works fine for pages and posts that include images. It’s just pages and posts that are all text that won’t work. It won’t even pull the logo from the top of the page.

My share buttons are provided by a plugin called Social Media Feather, version 1.8.4 (up-to-date). I’ve tried deleting the plug-in and reinstalling it, didn’t help. I’ve never had trouble with the plug-in before. I checked the settings, and while I don’t understand what most of them mean, I didn’t see anything that seemed relevant to the issue; but I’m an amateur, it’s possible I’m just ignorant and don’t have a setting right.

I’m using up-to-date Firefox 59.0.2 on an up-to-date Windows 10 OS. I’m running WordPress 4.9.4., which should be the latest version. I tried using Microsoft Edge and had the same issue, so I’m disinclined to think it’s the browser.

It’s a minor problem, but I’d really like to be able to share pages and posts without images like I could before.

Let me know if you need more information, thanks.

The page I need help with: [log in to see the link]