When testing promotional offer purchase in the sandbox environment, an error occurred.

Testing Promotional offer purchase in sandbox environment, error reported below:

Purchase did not return a transaction: Error Domain=ASDErrorDomain Code=500 "(null)" UserInfo={NSUnderlyingError=0x282752dc0 {Error Domain=AMSErrorDomain Code=301 "Invalid Status Code" UserInfo={NSLocalizedDescription=Invalid Status Code, AMSURL=https://sandbox.itunes.apple.com/WebObjects/MZBuy.woa/wa/inAppBuy?REDACTED, AMSStatusCode=500, NSLocalizedFailureReason=The response has an invalid status code}}, storefront-country-code=JPN, client-environment-type=Sandbox}

The steps are as follows：

1. Receive the nonce, signature, and timestamp from our app server.
2. However, the error occurred when I initiated a purchase request.

let result = try await product.purchase(options:[.promotionalOffer(offerID: offerID, keyID: keyID, nonce: nonce, signature: signature, timestamp:timestamp)])
switch result {
            case .success(let verificationResult):
                switch verificationResult {
                case .verified(let transaction):
                    return .success(transaction)
                case .unverified(let transaction, _):
                    return .unverified(transaction)
                }
            case .userCancelled:
                return .userCancelled
            case .pending:
                return .pending
            @unknown default:
                return .other(detail: "unknown error")
}

Is it because promotional offers cannot be tested in the sandbox environment?