First, you need to check the status of the inverter. 

If your inverter is in error (red light on the LCD screen), then you must go and retrieve the inverter's error codes. To do so, follow the procedure described in the following link: Error code recovery

Once you have recovered the codes, identify those that appeared recently (during the last 30 days) and refer to the following article (I have an error code IDXX and don't know what it means ?) to understand the origin of the problem.