How do I clear the cache for this plugin?

It’s not the plugin that is caching the image but Facebook. Facebook only fetches the URL once, then caches it for future requests, they clear the cache when they want. You can use the Facebood debug tools to check the real data fetched:
https://developers.facebook.com/tools/debug/

I used the debug tool and I get the error:
Error parsing input URL, no data was cached, or no data was scraped.

And it still shows a cached image

Is this happening because my image size is too small?

Maybe you can check, this is the url I am trying
https://www.jozepfit4life.com/effective-and-easy-strategies-to-stick-to-your-diet/

The image should be a bathroom scale

Hey! I guess it was because of the image size. I replaced it with a large image and now it’s working. This is solved

Glad to know it was resolved. We’d be extremely grateful if you could leave a 5-star review, thanks!