Redirection not working (only for /)

I have a wordpress site: bnbm.uk

and I want to use this along with this plugin as a url shortener.

I have a redirection set up, but it is saying 404 not found.

This is correct, as the page does not exist, but I don’t want to create a page for every redirect.

I have my dns set up through cloudflare. and im hosted with cloudways if that makes any difference?

Any redirect I create, other than / (root) gives me a 404. What could be the cause of this?

The page I need help with: [log in to see the link]