HI Steve
1. OPC tags status is always good for machines which are running, off course status is bad for few machines which are under shutdown. The PLC's are not communicating as their power is off.
2. In kepware error message comes when machine is under shut down as at that time PLC is also Off. Message is like this
"9/11/2015 10:05:45 AM Warning Siemens TCP/IP Ethernet Device 'Acid Filler-2.PLC1214' with ID 10.10.75.13 is not responding."
3. PCo is not generating any logs giving error
4.No I haven't. Please provide link, where i can get latest Service Pack, procedure to patch details etc.
With warm regards
Vivek M