SSL error - apps.geocortex.com

When visiting https://apps.geocortex.com/workflow/designer/, I mostly get an error (ERR_SSL_PROTOCOL_ERROR). When I view the SSL certificate details in the 'Security' tab of the developer tools, the website is listed under 'Unknown / canceled'.

We also have the same issue when loading workflows in the viewer. The viewer tries to load the library at https://apps.geocortex.com/workflow/latest/dist/hosts/gvh/loader.js but fails due to SSL_PROTOCOL_ERROR.

 

 

This happens in multiple browsers, Chrome, Edge, IE and Firefox.

 

 

How can this issue be solved?