Why might Windows EFS not list a certificate from Trusted People?

I have an encrypted file.

I've added a public-key-only certificate (exported from another computer that had the private) to all of the following: Local ComputerPersonalCertificates Local ComputerTrusted PeopleCertificates Local ComputerOther PeopleCertificates Current UserPersonalCertificates Current UserTrusted PeopleCertificates Current UserOther PeopleCertificates

However, when I go to the encrypted file's Properties>Advanced>Details>Add, the cert I installed to all of the above locations still does not appear as an option. The only option I'm presented with is the current user's default certificate.

What am I missing? How do I add the other computer's pub in a way that allows me to encrypt a file for that computer to then decrypt? (BTW, I know I could use a third party tool instead, but I'm looking to understand or fix Windows' built-in functionality)