Different URL for page depending on path take – categories etc.

I have a small issue that I cannot work out how to fix.

For the first post I made on a new blog, when navigating to it via the category, the URL is give as https://www.motleyhealth.co.uk/22 whereas all the other posts have their title as the URL. I have gone through the settings and search for re-write problems etc, but cannot workout what is wrong. It should look like the other pages, e.g. https://www.motleyhealth.co.uk/martial-arts-dvds-instructional-videos

Any suggestions would be welcome. I am thinking that I may just resort to deleting the pag and making a new one!