A master record for &1/&2 exists only in &3

What causes this issue?

You want to use cost center &V1& together with activity type &V2&. For
this combination, however, only one master data record was created in
fiscal year &V3&. The master record is defined in CCA during activity
type planning.

How to fix this error?

Create the master data record.
<DS:TRAN.KP26>Activity type planning</>
Or, check your entries.

Error message extract from SAP system. Copyright SAP SE.