Single phase two MP2 5000 connected with exact same length cables between AC outs and also same length cable between AC ins. 6 x US3000 Pylontech batteries and Cerbo with 12 x 500W PV panels. All been working perfectly for possibly around 2 years now. System did have connection to the grid for when no solar energy, grid supply was to both AC ins and it charged the batteries when turned on. All worked well. Grid supply was removed some months ago and a 6.5 kW diesel generator with AVR, supplied as suitable for PV systems was purchased. Due to current bad weather, the generator was connected to the two ACins via the same wiring as was used previously for the grid. When generating, the Master MP2 shows fixed LED for inverter but fails to even indicate presense of AC, ie green AC Mains LED does not light up (AC in is present, as measured with test meter, AC is at the ACin terminal, voltage is same to within +/- 1 volt and frequency shows same as inverter output within +/- 0.5Hz) .Slave MP2 shows flashing mains LED and flashing inverter on LED.
I have tested the generator onto an external load, it is working and very stable output, no discernable fluctuation in voltage or frequency by turning on a 3kW electric fire.
I have checked all the settings, tried several options, but nothing seems to allow the Master MP2 to indicate the presense of correct voltage at its ACin terminals.
What is so weird is that it did work a year ago, with same wiring, but using grid supply. This information may be confusing the issue and obscuring the problem
(Apologies to readers, the use of the terms Master and Slave is intended purely and only for engineering context)