The Migration assistant offers to migrate your existing signing identity, *at the condition that you give it your macOS session password* to access the Mac's secured keychain, in which your private keys are stored. If you declined to give it your session password, the Migration assistant won't be able to migrate your private keys. You'll only get useless certificates and provisioning profiles, because without their associated private key nobody can use them to sign anything.
This information was already given in the forum.
Next time, please include the necessary required information to your request. "last one" is not a version number. People who read your post next month or next year will have no idea which version number you're talking about.