You must specify valid values for the A3, P3, and T3 parameters for a subscription button

You must specify valid values for the A3, P3, and T3 parameters for a
subscription button

I used to use the following code for Paypal dropdown subscriptions using
BMCreateButtonReq. But in the past 30-60 days it started to fail with
asking for A3, P3 and T3. I tried adding these fields as dummpy fields,
but it did not work. How can I get it back up and running?
foreach (var p in pricings)
{
var optionSelectionDetail = new OptionSelectionDetailsType()
{
OptionSelection = string.Format("{0}", p.pricing1), //
a little risky but makes paypal form look better
Price = Math.Round(p.price, 2).ToString("N"),
};
if (p.months != null && p.months > 0)
{
var installmentDetails = new List<InstallmentDetailsType>();
installmentDetails.Add(new InstallmentDetailsType()
{
BillingFrequency = (int)p.months, //
BillingFrequency doesn't work
BillingPeriod = p.months == 12 ?
BillingPeriodType.YEAR : BillingPeriodType.MONTH,
//TotalBillingCycles = 20,
// Amount = optionSelectionDetail.Price,
});
optionSelectionDetail.PaymentPeriod = installmentDetails;
}
selectionDetails.Add(optionSelectionDetail);
}