When using DigiCert for certificate generation, they will supply you with a .CER or .CRT certificate file as the default.

The Titan/Cornerstone Certificate Management system requires a .PEM file format when Updating the CSR and attaching the certificate.

To acquire a .PEM formatted certificate from DIgiCert, review the process on the DigiCert website.

Note: when given the options for downloading a PEM file, choose "Single PEM File Containing Only The End Entity Certificate"