H.Tannous

Hi I have three orientations and would like to use 1 invertor with 3 MPPT inputs for that but I am not sure how to assign a single invertor to all three subarrays. I tried selecting the same invertor for each orientation with 3 MPPT but kept getting the following message: "you should define at least one string per inverter or MPPT input? Can you please advise? Kindly, Hadi