CONTACT IN OPTISTRUCT

Hi Everyone 

i am doing a static analysis in optistruct using contact. i have create two contact surface and also assign the contact but i am gating  this error.

Messages for the job:

 
 *** ERROR # 1761 ***
 Undefined SET # SSID on CONTACT 7.

plz help me out what is the meaning of this error.

Regards

Noor Alam