Selected plants are invalid for this purchasing organization

What causes this issue?

The purchasing organization of the plant differs from the purchasing
organization of the target reference plant. Assigned plant and
reference plant must belong to the same purchasing organization.

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?

Reassign the plant to another reference plant that belongs to the same
purchasing organization; use help list to see all available reference
plants.

Error message extract from SAP system. Copyright SAP SE.