white page when trying to set wp-creativix as default site theme

I am new to this, am creating my first multisite with Buddypress. It has all been going reasonably smoothly, any problems I have resolved through searching forums such as this one. But this one has got me a bit stumped.

I have set the default theme to be WP-Creativix by adding define('WP_DEFAULT_THEME', 'WP-Creativix'); to my wp-config.php file.

A site created with this shows a white page http://www.holistic-wales.co.uk/testsite/

A site I have manually edited to show the theme is fine http://www.holistic-wales.co.uk/testsite2/

(these are just test site at the moment so there is no content in them)

Also, and I don’t know if these two issues are related, but I have noticed this on today as well

When I am in the network admin dashboard I am able to create a new site, but when i am in the site admin for the network hub site (http://www.holistic-wales.co.uk) I get a

“Sorry, we can’t find the content you’re looking for at this URL. Please try selecting a menu item from above or to the side of this message to get where you’d like to go.” error

Please note, the url doesn’t bear any resemblance to the nature of the site, this has been my set up site (I didn’t think I would be without a proper url for this long!)

Thank you for any help!