Requirement to Obtain Approval of Overtime Payments

I am unaware of any requirement (nor does our contract contain one) to get Contracting Officer approval of overtime payments under a FFP contract with progress payments. One of our progress payment vouchers is being audited and the ACO is stating we should have obtained approval to include overtime in our progress payment request.

I am aware of FR 52.222-2 but according to its' prescription copied/pasted inbelow it is N/A to a FFP contract and our contract, appropriately, does not include it.

Prescription: The contracting officer shall include the clause at 52.222-2, Payment for Overtime Premiums, in solicitations and contracts when a cost-reimbursement contract is contemplated and the contract amount is expected to exceed the simplified acquisition threshold; unless --

(1) A cost-reimbursement contract for operation of vessels is contemplated; or

(2) A cost-plus- incentive-fee contract that will provide a swing from the target fee of at least plus or minus 3 percent and a contractor’s share of at least 10 percent is contemplated.

Does anyone know anything contradictory to what I have written above?