Unable to get www. working

Hello there. I’m having a lot of woes with my custom domain setup. I seem to have no issues with the basic domain working after following the setup wizard. So my domain, without the “www” works fine.

However, the “www” version appears to work on my desktop Chrome browser, but will not work on mobile at all. Instead I get a Cloudflare error message, attached.

Any help would be hugely appreciated!

I also attach a screenshot of my current DNS settings in Namecheap.