Note: New models of the MultiPlus-II do not have this problem - this article is now just here for historical reference
There is an issue specific to early releases of the MultiGrid product line (the original name of the new MultiPlus-II product series), when used in AS4777 environments.
These units support 'DRM' (Demand Response Management) under AS4777. This is a mechanism where a dry-contact input (AUX1) of the inverter/charger is used to disable inverter/charger operation via an external signal (e.g. from a grid operator).
Some early MultiGrid units were shipped from the factory with this function configured 'on by default' so that - if no action is taken and nothing is wired into AUX1 - the MultiGrid will simply not start up.
This is a very non-obvious failure mode - there are no error indications - and no LED front panel indications - and... nothing starts up (no AC output, no DC charging)
The MultiGrid is still visible as an element nn the CCGX screen - but it is shown as 'Off'.
In the MultiGrid sub-menu on the CCGX there is visible AC input voltage and frequency but the AC input source is shown as 'Disconnected' as per the screen shot below.
The remedy is to disable DRM0 operation in VE.Configure. This is under the AS4777 options sub-tab (or you can connect a 10k resistor across the AUX1 hardware input). This is documented in the Victron manual for the product but it is hidden away - not called out specially at all. So it wasn't easy to find...!