SAP Message QP505 - Unit & cannot be converted in header unit of measure &

Diagnosis
When an inspection lot is created with this plan, the system must beable to convert the sample unit into the corresponding material unit ofmeasure. This is not dependent on the conversion of the sample unitinto the unit of the plan header.
Since the sample unit cannot be converted into the unit of the planheader, it is possible that you have made an entry error.