@Pete B
Did I nail the terminals? If you have an ohmmeter check the continuity between Neutral In and Neutral Out, I would bet that they are connected inside. In that case you need only one connected to the neutral buss in your AC Buss
My Magnasine MS4024AE is a very similar design, they use only one transformer that serves as both charger and inverter. The connection of the neutral does not need to be broken when switching from charger to inverter. There is a 2 pole relay that shuts off the input in inverter mode. In standby mode this relay connects L1 in to L1 out and L2 in to L2 out to provide passthrough power.
These inverters were designed by the same folks....If you can read schematics I can email you my manual which does show the internal basic wiring that Schneider will not show you. They will not be exact, but you will get the picture of how they accomplish things. Its not a full detailed schematic, more of a basic layout of the transformer and charger/inverter. Its setup for the layman to understand
Also has the best grounding system layouts that I have ever seen.
HAPPY NEW YEAR......