Items in the requisition list that are grayed/greyed out are typically already included on a purchase order, and cannot be selected to prevent duplicate item orders from being placed. Ensure that no active purchase orders or purchase order drafts have the requisition items placed on them. This could also be due to having items associated with particular suppliers. You can only create purchase orders where items can be obtained from the same supplier.

In order to have this changed, you can select the option "Don't associate items with suppliers" option in your branch profile.