I recreated all the single user projects, by exporting the HW configuration of each single user project, copying the blocks and recreating all the NetPro's. Then I was able to go online via CP1613(ISO), in each of the single user projects.
Then hopefully, I merged all the single user projects into one multiproject (like they were before), merged all the necessary ethernet and profibus subnets. But, then I got a new problem. One of the single user projects was not going online. So, I revert back to the old configuration of a single network, connected the Engg Station to the network via its own motherboard NIC and disabled the CP1613 from the device manager. I selected ISO access path of the motherboard NIC as the S7ONLINE Set PG/PC interface. But then again, UNFORTUNATELY the S7ONLINE interface changed to CP1613(ISO).
I am feeling helpless with the situation. Please somebody help me urgently.