Plugins will not create / show thumbnails

I’m having a rather annoying issue that I have been facing on two different WordPress sites that I have been developing that I can’t seem to figure out a solution anywhere.

Any type of photo gallery or portfolio plugin that I try simply will not create or show a thumbnail.

So the gallery display page will be all of broken images or if it’s smart enough like the portfolio one I tried most recently show “No Photo”.

I tried to work around this by choosing a image that’s already uploaded in to my media and already has a thumbnail. But nope, that doesn’t work either. Still I am left with broken / missing thumbnails.

I figured it might be something to do with my host, but it’s happening on two different hosts.

Does anyone know how to start trouble shooting this issue or know what might be causing it?

All other sizes of the images work except for the thumbnail it self.

Thanks