I have gone through my setup of demand planning a few times and when I try to calculate item demand plans I have no items to choose from after filling the required fields. I am new to the company but I know when sales orders and work orders get entered it's with the bare minimum, could that be affecting my list?

Did you set the item to use MRP as replenishment method?

that worked! So can I do a MASS UPDATE on that field for the rest of my items?

yes