When users encounter a greyed out Integrated Shipping Label checkbox, consider the following:
1) If Pick, Pack, Ship feature is enabled, verify the status of the item fulfillment. If the status is set to Picked, then the checkbox for Integrated Shipping Label is greyed out. It can only be checked if your Item Fulfillment status is either Packed or Shipped.
2) Verify the Shipping Item if the Shipping Label Integration checkbox is marked. If this is not marked, the Integrated Shipping Label on the item fulfillment is necessarily greyed out even if the set status to Packed or Shipped.
Note: The change has prospective effect. Marking the Shipping Label Integration in the shipping item records does not update the item fulfillment transactions made prior to the said marking.