Dunning activity not defined for dunning level &2 in dunning proced. &1

What causes this issue?

In dunning level &V2& in dunning procedure &V1&, no dunning activity
has been defined with amount limit zero and creditworthiness zero.
The data was saved or had already been saved. The system issues an
information message.

How to fix this error?

For each dunning level, define a dunning activity with amount limit
zero and creditworthiness zero. You can also use an empty dunning
activity defined with the function module FKK_SAMPLE_0350_ACTVT to do
this.

Error message extract from SAP system. Copyright SAP SE.