Exception while creating Key DTO error while uploading trusted root certs

Private key: No password protection, .key file
Public certificate: .crt file, server certificate
CA certificate/Chain: .pem file, includes intermediate crt followed by root crt

During import getting Exception while creating key DTO. 
* The .crt public certificate and the .key file has the same MD5 checksum. 
* .key file is not password protected
verified with openssl commands.