Please……Post the name and model of the unit……..
Search for the manufacturer……MOST have instructions online at their web-site………..
Remove the unit and “DO IT” again……..take the motor housing off and check the wire terminals…..motor rotation……..duct openings/obstructions/alignment…..
How is it mounted ?………Modern units made to fit “all” situations often have subtle adjustments necessary to operate correctly in different configurations………Some units just hang over the stove……others built-in……
Plug it in on the “bench” and see which direction (and If !) the vent motor is blowing………
remove the “plastic wrap” from the stainless steel grease filters ? all the cardboard packing ?