Hi Tracey,
strange indeed.
It's not Alxposts issue, since I see your featured post thumbnail is also not working.
What first comes to me:
-Have you recently installed any new plugins?
-What version of Hueman you are using?
Try deactivating (not deleting) all plugins 1 by 1 - first less important ones - and see if it will start to work proper at some point.
PLS do this and LMK how it goes.
Cheers,
Mike