Incorrect attribute '&1' in variable '&2'

What causes this issue?

The variable is to be replaced with the value of an invalid attribute.

System Response

This is an error message.
Variables cannot be used if they are to be replaced with the value of an
invalid attribute.

How to fix this error?

Replace the invalid attribute with a valid attribute.

Procedure for System Administrators

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

Error message extract from SAP system. Copyright SAP SE.