I am trying to create Client Certificates Authentication for my asp.net Website.
In order to create client certificates, I need to create a Certificate Authority first:<
I just had this issue today and feel compelled to post my solution in the hope that you will lose less hair than I've just done.
After trying the solutions above, we had to re-issue the SSL certificate from the SSL provider (RapidSSL issuing as a reseller for GeoTrust).
There was no cost with this process, just the five minute wait while the confirmation emails (admin@) arrived, and we gained access again.
Once we had the response, we used IIS > Server Certificates to install it. We did not need the MMC snap-in.
https://knowledge.rapidssl.com/support/ssl-certificate-support/index?page=content&id=SO5757
We kept a remote desktop window to the server open throughout, to avoid any issues with differing login accounts/sessions, etc. I do believe it is an IIS bug as another expert believes, as we only have one RDC account. What is most infuriating is that the very same certificate has been working perfectly for two months before suddenly "breaking".