Error calling FM <SBCOMS_SEND_REQUEST_CREATE> in <SO_DOCUMENT_SEND_API1>

Hi All ,

Getting an error 'Error calling FM <SBCOMS_SEND_REQUEST_CREATE> in <SO_DOCUMENT_SEND_API1> with SY-SUBRC <1> ' while executing a custome function module for sending email as PDF attachment . Please help me to resolve this error.

Thanks In Advance .

Regards,

Sijin K P.