Please select a valid field in list

What causes this issue?

The cursor is positioned on a field (&V1&) which is not linked to a
function. The reason for this may be as follows:
The cursor is
on an invalid line (e.g. list header)
not on a field in the list display
on a field in the list display which is not linked to a function.

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?

Please place the cursor on a valid field.

Error message extract from SAP system. Copyright SAP SE.