Error:14094418:SSL routines:SSL3_READ_BYTES:tlsv1 alert unknown ca (Error No. 35)

Error Time: When tried to send request to PayPal using curl/socket payPal Express and PayPal Direct Method we get this response as curl error.

Reason: Sending PayPal API Certificate or (API Username and API Password) value is not valid.

Solution: Make sure that your PayPal API Certificate or (PayPal API Username and PayPal API Password) is proper/valid and in proper location/path.