Cannot Create Work Order From Sales Order

Hi All,
I am having an issue where I cannot click the work order box on an existing sales order to create a workorder. The work order box is greyed out.
Does anyone know why that would be?
It is only happening for one specific customer and I cannot figure out why.

On the item record for the items on each Sales Order line there is a native checkbox field called ‘Special Work Order Item’. Go to the Item record set that to True and save the item. Go back to the Sales Order in View mode and under the SO line you should now be able to click the “Create WO” link.