Seed CAN BUS Shield Extended Format

Arduino Uno R3, Seed CAN BUS Shield V2, 250K baud, INNOMAKER USB-CAN converter (Program: Examples/CAN-BUS Shield/Send Receive).
Question: I am able to send standard messages from USB-CAN converter to UNO and verify receipt in the UNO. When I switch to extended message format, UNO no longer receives messages.
I see a format designation in the send command but I don’t see any such setting for receive (Extended).
CAN_SEND.sendMsgBuf(0x600, 1, 8, stmp);
Is there more to this story or am I missing something basic?