404 error pages not showing on sub domain

Hi guys,

Hoping someone can help.

We have recently noticed that one of our sub domains 404 errors are not working, when we try to access a page that doesn’t exist it just gives us a blank page. Rather than a user friendly/seo friendly 404 error page. Is this due to it being on a sub domain? Our main domain 404 errors work perfectly fine.

I’ve also looked at the permalinks and they’re all set correctly too.

We are using the Bridge theme.

Thanks in advance.