Error for periodic boundary in GAMBIT
 

I would like to simulate 3d flow around circular/square cylinder using periodic boundary. To make periodic boundary, it requires to link face mesh. When I try to link face mesh in GAMBIT, I got following error. Does anybody have suggestion to solve this problem?

command> face link "face. 2" "face. 5" edges "edge. 1" "edge. 7" vertices "vertex. 1" "vertex. 3" periodic

ERROR: There must be one edge specified for each face loop

Thanks in advance Karim