The IP should be the PUBLIC IP for your server. Not a Private one.
Can you reach your public IP from the public internet? Like from a different device, perhaps a mobile phone with wifi disabled, try reaching
http://public-ip/
or
https://public-ip/
Because the 522 means a connection failure from the Cloudflare Edge to the public IP you setup as proxied.
Getting this working is probably better handled at the Cloudflare community.
No requests work to your origin server. You need to have a working comms setup before being able to use a Let's Encrypt HTTP Challenge to get a cert.
# This works as Cloudflare handles HTTP request and redirects it
curl -i http://1renner1.uk
HTTP/1.1 301 Moved Permanently
Location: https://1renner1.uk/
Server: cloudflare
# Following that redirect for your "home" page fails
curl -i https://1renner1.uk
HTTP/2 522
server: cloudflare
# HTTP requests like the ACME Challenge fail in same way
# Looks like you setup a page rule to exempt redirecting these to HTTPS
curl -i http://1renner1.uk/.well-known/acme-challenge/Test404
HTTP/1.1 522
Server: cloudflare
For page / cache rules and the ACME HTTP Challenge below is a good reference. But, that isn't your immediate problem. The 522 for HTTPS "home" page indicates the basic comms problem. Note linkp is a MVP at the Cloudflare community: