What causes this issue?

In the graphic, you have either selected no points or more than one
point. However, only one point can be selected.

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

System Response

How to fix this error?

Use the mouse to select a point, for which you wish to display details
and call the desired function again.

Error message extract from SAP system. Copyright SAP SE.