SAP Message 56739 - Accomm. deduction only allowed with accommodations per diem! (TripNo: &)

Diagnosis
You selected a deduction for gratuitous accommodations, but not
per diem reimbursement of accommodations.
The deduction is only considered if per diem reimbursement ofaccommodations is active.

Procedure
Select the 'P' field for per diem reimbursement of accommodations.