Not a valid template

Hi, I’ve changed host but ever since I get this [Not a valid template] in place of my galleries.
These are the pages
http://www.artbykarie-ann.co.uk/galleries/dog-portraits/
http://www.artbykarie-ann.co.uk/galleries/cat-portraits/
http://www.artbykarie-ann.co.uk/galleries/horse-portraits/
http://www.artbykarie-ann.co.uk/galleries/animal-portraits/
http://www.artbykarie-ann.co.uk/galleries/wildlife-art/
http://www.artbykarie-ann.co.uk/galleries/bird-art/
http://www.artbykarie-ann.co.uk/galleries/aceo/
http://www.artbykarie-ann.co.uk/pet-portraits/process/

I’ve contacted siteground and this is what they said
After thorough investigation, I noticed that the path to the template was incorrect (was the path on the old host). I updated it to NextGEN Legacy: gallery-caption.php (Gallery -> Gallery Settings); however, this did not fix the issue. I have checked several WordPress topics on this issue:

https://wordpress.org/support/topic/not-a-valid-template-2
https://wordpress.org/support/topic/template-absolute-path-and-migration-to-other-hosting
https://wordpress.org/support/topic/nextgen-gallery-not-a-valid-template

It seems that this is a common issue after moving from one host to another. The plugin authors recommend resetting the gallery settings (Gallery -> Other Options -> Reset Options). If the issue does not get fixed afterwards, I would advise you to contact the plugin developers/community for further assistance.

I’ve followed the links they suggested, deactivated and deleted the plugin, uploading it again. the images were retained. I’ve viewed them through my ftp and they are where the path says but still not showing up on my website.
Can you offer any help please as I don’t want to use another gallery plugin.
Many thanks.

https://wordpress.org/plugins/nextgen-gallery/