@sticilface I thought you could only have one CT too, then I spotted someone else’s post who had used two. However they didn’t explain how things were configured. That led to a lot of ferreting around and I discovered that you can have one CT on the Grid connection and one on the Aux Input (both on the Multiplus). You can choose other inputs but this is the one that worked for me. The latter requires the AC Current Sensor Assistant to be loaded. The Grid CT is just a standard CT but the second one must be the Victron device.
My system is proof that two CTs can be installed. I think if you click on my name you can see it operating. It is only a very simple system. 16kW Seplos battery with a Cerbo GX, a Multiplus ii and 4 kWp of solar connected to a SMA Sunny Boy inverter. I also have a PV Diverter that sends excess solar to my immersion heater. The latter device is one designed by Robin Emley.
I should add that when setting up my system I had strange values on my display that I struggled to resolve. Things like the AC loads would go to zero or the PV figure would be deducted from AC loads. Eventually I discovered that after doing any downloads or configuration activities I needed to shut off both my Cerbo GX and the Multiplus by their mains switches and restart them. My system still suffers from this issue today. I just downloaded the configuration file to upload an image of the Assistant settings, for this post, and then noticed that my display was wrong again. That triggered the memory. I shut the units down and restarted them and all is back to normal. That is just from doing a download and not doing any configuration at all.