Cannot Find The Original Signer – P7B Certificates In IIS

When trying to install a p7b certificate in IIS, I get this error:

Import Certificate

There was an error while performing this operation.

Details:

Cannot find the original signer

This is most likely because you haven’t installed the PFX part of the certificate chain. To fix this, install the PFX certificate with the private key associated with it instead.

I don’t believe the following is correct, but I also found notes on other websites saying that IIS cannot find the original signer because it doesn’t know the friendly name of the certificate. To fix this:

1. Right click the p7b certificate and click Install, following the wizard (defaults are fine. I also installed it a second time, specifying that it should also be installed into the Trusted Root Certification Authorities)
2. Open an MMC console and add the Certificates snap-in, specifying the Computer account.
3. Navigate to Personal -> Certificates
4. Right click the certificate that is giving the Cannot find the original signer error, that you are trying to install in IIS. Then click Properties then enter a friendly name for the certificate.

   ❗ On the General tab there should be a key icon with the following message:

   You have a private key that corresponds to this certificate

5. Finally, you should be able to bind the certificate to a website in IIS

I don’t believe that the above steps are correct, I still think the fix is to install the PFX part of the certificate (with the private key associated with it), but if you find the above useful, please let me know.