I am getting the following error when trying to create a new certificate. Please can you tell me why I am getting this error? My existing certificate is not detected by the control panel/server.
It's saying you already have a valid cert. See the "Testing and troubleshooting" option win-acme
You should really figure out first why the cert that you did get isn't working - most likely whatever control panel software you are using (?) is not configured to use the new cert. win-acme will deploy to IIS ok but it doesn't understanding other pieces of software and it can't auto configure them, sometimes you need to script that yourself once you have the cert files.
It also looks like vehicleland.co.uk points to a web server that's hosting hundreds of other websites and currently points to a landing page. Is your domain pointing at the correct IP address?