question

It looks like a Modbus coms issue...

Have a look at the Modbus baud rate and unit address in the meter and make sure the settings match in the CCGX, if they don't correct the settings so that they do, preferably in the CCGX, because it is the more flexible of the two, but provided both ends match it doesn't actually matter which you change.

Now check/note/backup all your system settings, preferably using VE Configure.

Power cycle the EM24

When you have done all that, run a 'system redetect' on the on the CCGX.

Set the meter role you need and see if it keeps that role, if it doesn't you probably have a physical problem either with the dongle or the meter.

Lastly... Open two VE Configure instances, one to show you the backup, and the second, connected, that you will use to download, manually alter, and then upload any/all settings that are not correct.

doing this with the inverter off is a good idea.

@Janefinch

There is also the possibility that the CCGX is having age related issues.

It may be time for an upgrade.

It wouldn't be hard to test the meter. plug the USB/RS485 into a computer and run a Modbus test program. Many are quite expensive but Schneider do a reasonable one, free, that can handle single and spanned requests on all typical Fc's.

I do not know about the CG EM24 specifically, but its bigger relatives , EM 26-96 for example, will only accept a query for a limited number of registers, 12 I think, so 24 bytes, in a single read.

The docs are easily to find and download from CG, and pretty well laid out in my experience. The CG versions of protocol docs 'may' be easier to use, if testing outside a Victron ecosystem, I cant comment on what Victron distribute info wise but the CG versions are more than adequate when looking at come in general.

I used to use them, EM26-96, extensively because the MID version was relatively inexpensive and capable, but I generally go with ND meters now, for the same/similar reasons.

Looking at the CG website it appears the range has expended considerably, since I last checked, with far more Modbus TCP offerings, so I am probably a bit out of date, in many ways:-)