While doing an emergency wildcard SSL certificate replacement on a web server farm, most servers would allow me to select the certificate after the import but a handful wouldn’t. It was a bit random but the fix was simple enough.
After importing the certificate with the private key in IIS Manager and editing the SSL bindings for the site where it needed to go, when I selected the newly imported certificate I got this error:
There was an error while performing this operation.
Details: The specified logon session does not exist. It may already have been terminated. (Exception from HRESULT: 0x80070520)
There are a lot of other people getting this error for a whole host of reasons with different fixes. Your mileage might very with one.
Remove and re-add the certificate from IIS Manager.
In the three cases where I saw this issue, it resolved each time.