If you received only a CER file, it means your
Code Signing Certificate is missing the private key, which is required for signing. Previously, some providers like GlobalSign and Sectigo used browser-based issuance, where the private key was generated locally and had to be exported along with the certificate. Now, many providers require a USB token for
EV Code Signing Certificates, while OV certificates can still be exported as a PFX file. If you don’t have the private key, check the machine where the request was made or contact your provider for a reissue.