A 2.4 Kw inverter is serious equipment costing quite a lot of cash - rather too much cash to take a chance with. The very fact you have to ask how to fix it means you probably shouldn't touch it but should entrust the repair to a properly insured professional.

I suggest you check the literature provided or visit the manufacturer's website for advice, make whatever checks you can regarding external connections and wiring and then find a repairer.