I actually received a positive response:
Please accept our apologies as we were unable to adjust your reservation to reflect your free night on August __, 2017 (one night) at the Holiday Inn Hotel & Suites Orlando SW - Celebration Area. In order to fulfill the Best Price Guarantee promise of providing a free night stay for confirmation number ___________, we will reimburse the amount paid through a US Dollar (USD) denominated check via mail. In line with our Terms and Conditions of the program, the check shall be sent out the address listed on your reservation.
Then today I receive:
We understand that we have initially advised you that we will reimburse the amount you have paid during your stay at Holiday Inn Hotel and Suites Orlando SW - Celebration Area last August __, 2017 through a US Dollar (USD) denominated check via mail. However, upon attempting to process the payment, we reviewed that the hotel made the necessary adjustment. Thus, please be advised that the reimbursement is no longer forthcoming from our office.
The only problem is that the hotel charged the prepayment for my room to my credit card in July and has never refunded it. And now, IHG is not responding to my emails.