Specify a valid function code (&2 does not exist)

What causes this issue?

You have entered the function code '&V2&'. However, this code is not
defined in action group '&V1&'.

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?

Enter a function code that is defined in the action group '&V2&'.

Error message extract from SAP system. Copyright SAP SE.