There is a RJ45 connector inside the phoenix multi. I connected it via LAN cable to the cerbo GX, to be precise to one of the VE.bus ports. But when I do that, the phoenix multi turns off. Why? I want to see my inverter in the remote console and in the VRM.
Is this a Phoenix inverter? Or an older inverter charger?
hat is the model #, and the firmware version.
Yes, inverter of course.
For the firmware version I might need to connect my mk3-usb-device and connect it to my computer. Or is it possible to see elsewhere? Can it be updated?
I have the same problem but with a 24/3000 Phoenix inverter. I was wondering if you ever was able to solve the problem?
It’s in the manual
https://www.victronenergy.com/media/pg/Cerbo_GX/en/connecting-victron-products.html#UUID-45296fbc-6298-b29c-2e54-7730edc3d313
As my device has a 17… firmware (which you can see on the lengthy chip on the first photo), it is not compatible. The solution is to buy a VE.Net to VE. Bus converter.
Product description:
Here
Quite expensive. 
Here for half the price Victron VE.Net to VE.Bus Converter — Trans Marine Pro & Solar Solutions Northland