How is URL for new content page determined?

In shopware 5.5, I have created a new page in Content>Shop pages. It is called “test page”. I assigned it to the group “General”.

In link address field I entered https://www.thefishsociety.co.uk/test-page/

I cleared the cache.

But when I go to the above URL, I get “Sorry, the page you are looking for cannot be found”

How do I set URL for my new page?

The link address field is for linking to an external site.

The urls for your content pages are managed globally in the SEO / Router settings > Cutom site SEO URLs template: 
https://docs.shopware.com/en/shopware-5-en/settings/seo#seo-router-settings