Thumbnails are only partially created (greyed out)

Is your Jigoshop plugin up-to-date? Are you using Jigoshop Official CSV Importer? Please post your System Info here for us to look into.

Hi Jakub,

Thanks for the response. I’m using a wordpress theme that may not allow for updating.

WordPress 3.8.5
Jigoshop 1.8

I’m attempting to import a large amount of products (18000)

Hello and apologies for the delay.
Does this also happen when you try to add only a few items (not 18000)? You can try switching temporary to another theme e.g. Simply Jigoshop to see if the problem is theme related.
But most probably it’s because of your very outdated Jigoshop and WordPress version, we highly recommend updating them on a constant basis. When upgrading to 1.15.2 we suggest you make a backup copy of your database in case something goes wrong.