Conversion factor in purchase order &1 &2 could not be determined

What causes this issue?

The conversion factor between the order unit of measure and the base
unit of measure is not maintained.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Check the details of the purchase order item.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.