Hog 4 CITP with Media Master Pro not working

I'm having an issue with CITP media previews not loading. Everything was working fine until I switched to a backup PC running Media Master, now I have the same issue with both PC's without having changed anything.
Specs are:
Hog 4 v3.6.0
Media Master Pro v 5.0.3
Media Master Full Layer 1.1 Extended

I am able to patch media to Media Master in the patch window and every time I refresh media, it says it is cached but there are no thumbnails.

Any thoughts as to why this suddenly stopped working?