It seems the Multi RS Solar 48/6000 does not publish any CAN messages to the CAN network, connected to Cerbo and NMEA out is on, but using NMEA Reader, do not see any CAN messages of Solar Output, AC Input, AC Output.
I wonder if this is something that has been missed in its functionality?
Is the data from the Multi RS available on the Cerbo? This means that the Multi RS does send out NMEA messages as those messages are also used by the Cerbo.
If the data is available, please check the filters in NMEA Reader whether they are setup such that they allow reception of the Multi NMEA messages.