IDX10803: Unable to create to obtain configuration / Http response error 406 Not Acceptable
When using Sitefinity's built in OpenID authentication (Identity Server 3)*, when trying to access Sitefinity backend an unhandled exception is thrown: IDX10803: Unable to create to obtain configuration from: 'https://<identity server domain>/Sitefinity/Authenticate/OpenID/.well-known/openid-configuration'. (Full exception below) Http response error 406 Not Acceptable * this authentication mechanism is deprecated since Sitefinity 14.4