Where have my categories gone?!

Just opened up my WP Admin panel after about a month (on a site that I’m developing) and noticed that the categories are missing in the Admin panel.

On the Admin page it clearly states that I have 13 categories and they also appear in the database in the wp_terms table but they are missing from the Admin page and therefore my site is currently broken.

I don’t want to go and do anything on the Admin panel or DB just in case it messes up anything else and there might be a simple solution that somebody knows about?

Any help would be greatly appreciated