No action possible (action group &1 not defined)

What causes this issue?

The action group '&V1&' on which your cursor is currently positioned,
is not defined in Customizing. For this reason, no actions exist for it
either.

System Response

No functions could be executed.

How to fix this error?

Make the necessary corrections in Customizing or contact your system
administrator.

Error message extract from SAP system. Copyright SAP SE.