You have too much power consumption on the AC Backup output of your inverter. You have appliances that require too much power at start-up or continuously.
Disconnect high power appliances immediately in order not to destroy the inverter electronics. You must respect the operating specifications of the inverter and not exceed them (maximum power & current on the AC backup output). If you regularly have this error, it is very likely that the IMEON is irreversibly damaged.
Once the wiring modification is done, you can press the OK button for 5 seconds to reactivate the AC Backup output.