What do you mean "from blockchain to coinbase"? From where you got that error message?
Hey Bro, do never use your private keys. Even i can't understand your issue but it seems you are doing some dangerous moves. Afaik, none would ask you for your private keys unless you are willing to migrate from a wallet to another but this option isn't available with coinbase wallet as far as i can remember.
Whatever, do never reveal your private keys! And do never believe anyone contacting you in private pretending to help you, he is surely trying to steal your keys.
You need to explain further your issue so we can help you.