newbie - modbus adapter not showing data points

[NormHenderson]

I hope this is the right place. I am trying to configure IObroker to pull data from a Victron CCGX over Modbus TCP. The instance connects but no data points are shown.

1. On the "general" tab, I don't see what is the purpose of the "Device ID" and the checkbox "Multi Device ID".
2. On the "holding registers" tab, what is the meaning of "Slave ID"? If I put a value (any value) there, then on the Objects page there is a line "Holding registers" but no sub-item and no value.
3. My objective is to store the data points from the CCGX in a log file. I need to analyze a particular low-voltage event. But I don't see anything in IObroker that will log data to a file? The "LOG" page seems to be just system information. The "EVENTS" page has lots of data but again no actual data points.

The Instance is defined: General: TCP, 10.1.0.40, port 502, Device ID 100, Multi device IDs checked, Use aliases checked. On the Holding Registers page, Address 3 (the register no.), Slave ID 246, Unit 246 (the correct Modbus Unit ID), Type Unsigned 16-bit Big-Endian, Length 1 Factor 1 Offset 0 Role value.

I will appreciate any advice, or pointers to documentation (what is on the site doesn't seem to cover this). Thank you!

[ssond0815]

@normhenderson If the instance connects, the whole problem is usually that not the right registers are configured. I do not have the Victron CCGX but you should carefully read the register documentation of the Victron device and set the right one up in the adapter instance. Regarding your question 2: In my "holding register tab" I cannot find a separate SLAVE ID information. What exactly are you referring to? ad 3: If you configured the right registers, you will find values behind the data objects.
I have to admit that the modbus is tricky if you are not familiar in the details of the protocol.