Problem moving WP site to https

I would like to make the WP site at https://captionpro.com.au:443/AlekaConsulting use https and be accessed by users entering captionpro.com.au/AlekaConsulting in their web browsers. I have purchased and installed an SSL certificate, which appears when I create a new https binding on the web site using IIS Manager on port 444. (I am prepared to use a different port number for the https web site, though I would prefer not to.) when I try and access the web site using https://captionpro.com.au:444/AlekaConsulting from a browser on the server hosting the Web site I get the message “This site can’t provide a secure connection”.
The purchased SSL certificate comprised 4 files namely

AddTrustExternalCARoot.crt
captionpro_com_au.crt
USERTrustRSAAddTrustCA.crt
USERTrustRSADomainValidationSecureServerCA.crt

I try and use a plug-in such as Really Simple SSL for the conversion is says that I do not have an SSL certificate installed. Clicking the button to reload over SSL shows the ‘This site cannot provide a secure connection’ message.

I successfully added all these certificates to the WebHosting certificate store via MMC->Certificates, and IISManager shows captionpro.com.au as an installed certificate for the web site.

The Web server also hosts an ASPX application bound to port 80. If I create an additional https binding to port 81, I can access the application via https://captionpro.com.au:81.

Can anyone suggest what I need to do in order to access my WordPress site via https?

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