What had worked? I use Windows 2012, but never had such a problem.
Your certificate has only one domain name ( https://check-your-website.server-daten.de/?q=jdcounselling.co.uk ):
CN=www.jdcounselling.co.uk
07.05.2019
05.08.2019
expires in 81 days www.jdcounselling.co.uk - 1 entry
So your non-www version isn't secure.
Domainname | Http-Status | redirect | Sec. | G |
---|---|---|---|---|
• http://jdcounselling.co.uk/ | ||||
217.68.242.220 | 301 | https://jdcounselling.co.uk/ | 2.057 | A |
• http://www.jdcounselling.co.uk/ | ||||
217.68.242.220 | 301 | https://www.jdcounselling.co.uk/ | 1.857 | A |
• https://jdcounselling.co.uk/ | ||||
217.68.242.220 | 301 | https://www.jdcounselling.co.uk/ | 3.106 | N |
Certificate error: RemoteCertificateNameMismatch | ||||
• https://www.jdcounselling.co.uk/ | ||||
217.68.242.220 | 200 | 3.314 | B |
Create one certificate with both domain names and use that with two bindings.
Or create a second certificate with the non-www domain name and use that (I don't know if your client has such options).