Iphone – Unable to create Apple Developer certificate request using keychain access tool

You can't install a certificate on a different machine that the CSR (cert request) was generated from just from the certificate. The reason is this stuff is based on asymmetric cryptography, also called Public-key crypto. The machine you generated the CSR on created a Private key, and stored that in it's keychain, but sent it's public key along with the CSR. When Apple generates the cert, they use your public key in the creation of the Cert. In order for you to use that cert, the machine must have both your private and public keys in the keychain. You can export your public/private keys from the original machine and import them on your second computer, and then you'll be able to use your cert on both machines. Note: it's very important you keep your private key private - don't share it with other users, don't put it on a public file share. Loose that and you'll have trouble. Look under "Managing your digital identities" for instructions on how to backup & restore your key pair.

Solution:

• In the code signing request (CSR) window, there would be a field called "Request is", choose the radio button corresponding to "Save to disk".

Reason why you faced the problem:

• By default the the "Request is" field is chosen as "Emailed to the CA".

Note:

• To get to the CSR window, open Keychain Access > Certificate Assistant > Request a Certificate from a Certificate Authority.

Refer:

• https://developer.apple.com/ios/manage/certificates/team/create.action