What causes this issue?

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

The system cannot display the object you selected or you have not
selected an object.

System Response

How to fix this error?

Position the cursor on a field offered to display object (e.g.
functional location number, equipment number, material number, order
number, customer number, etc.) and select the menu path again.

Error message extract from SAP system. Copyright SAP SE.