opc communication problem in plc500 vs digivis 500 during run time

dear all

i was configured redunant config in opc server. when i was written values in plc(AC500) it will be updated in digivis 500 but i was written values via digivis500 it does't update. why this type of error coming .so many times i was downloaded varibles via opc but same type of error comes . what is the resson behind this type of error ? i was fully confused ?

At the same time i was changed my config redunant into single plc it works properly .when i am going to redunant config again same problem .

Note: during my redunant config , some time it shows all variables some time it shows plc2 only active .(eg - plc2 com state ok like that) . Anyway it communicates to plc without showing any error but problem is i cant write values from digivis500.

please give me the solution for this problem