AlbertRN_21

I experienced exactly the same problems that you are having a few years ago. Sometimes there seemed to be a pattern to the faulty stations but despite swapping out various stations both digital in/out and analogue in/out and the BT11N the problem would always return at some random time. I had been assured by the electricians that they had carried out a terminal tightness check on all the stations prior to me being called to site. In desperation after a month of random failures I instigated another wiring check and found a loose connection at one of the stations that was particularly awkward to get to. I can't remember whether it was DA, DB or DG but once tightened the fault never occurred again.

Open your Q2 project and create a new connection, I've called it Ethernet_CCLink in my example. PC side and PLC side I/F should be set as per your Q3 project. Select "Other station [Single network]"  Double click "CC-Link" Head I/O is the slot address of the CC Link module in the Q3 rack Station number is the station number of the CC Link module in the Q2 rack. Connect to the Q3 via ethernet cable and select connection test and it should come up with "succesfully connected with the Q2"