Insert two MMPU board, then background connection is failed. It is good when insert only one MMPU board.
Turn off the second switch of the first MMPU board,then establish the connection,and set MMPU ip. And do the same thing to the second MMPU board. Notice that the two ip can not be the same. Now insert two board, and the connection is good.
Usually two MMPU board is factory setting, so their ip is the same, and lead to ip collision. Thus connection is failed.