Social media image problem

Hi there. I have a strange problem…. I had WPSSO plugin on my site as I was advised back in December but it was causing a conflict so I removed it. Once it was gone, I realised that my images were showing nicely when I shared my posts on Facebook so all was well.

Then! For some reason ONE of my sites has stopped showing the images and I can’t for the life of me work out why. I have two sites running Highend and both are essentially the same, but now one of them shares images and the other doesn’t.

I’m figuring it has to be a setting or something somewhere that I’ve inadvertently changed. Can you help???