Multisite Not Working – Members Sites Problem

The registration process works fine, but when another member visits their site, it has no styling and is using no theme. And then when they try to load the login URL, it doesn’t load at all.

Here is my site: https://www.special-ones.co.uk

Here is the registration link: https://special-ones.co.uk/wp-login.php?action=register

Please check it out for me and see if you can sort this out for me. I need to urgently.

Thank you!