the schengen visa rejected an alert that was issued in the shengen information system rejecting the entry of a member state

I applied for the Schengen tourist visa through the Italian consulate Karachi in July 2019, but received a rejection letter saying that an alert was issued in the Schengen information system with the purpose of rejecting the entry of a member state. I have the right to appeal in 60 days. Earlier I requested Schengen tourism in 2018 through the Netherlands consulate, but I rejected for common reasons the purpose of justifying the stay and there were no strong links. but my recent request was strong enough, but I got an unusual rejection reason. I don't understand what to do please help me