Hi thanks for the response, I really appreciate it.
I tried re-uploading from a backup I had as I have edited the theme quite a bit, and it hasn’t worked. Any idea why that hasn’t worked? Does it really have to be a fresh download? I hadn’t upgraded to the latest version of WP.
Just in case I did it wrong, I’m using Filezilla and I deleted the wp-admin folder then uploaded the wp-admin folder from a previous backup, then deleted the wp-includes folder and uploaded from a previous backup.