Unbilled Sales (Actuals) not picking up a price on Time & Materials Projects

When invoicing all our Time & Materials projects, no sales rate is being applied to the time entries, even though a sales Price List exists in the Project Price List containing the roles relevant to the Project.  

The Unbilled Sales actuals records show no Price.

The Chargeability view is empty and clicking on the 'Edit Sales Prices' button does nothing.  The Price List field simply shows 'Price List' and cannot be changed.

All suggestions would be greatly appreciated.