Promotional offer does not work, gave error code 3903

I tried to apply a promotional offer to a subscribed user.

When I tested it in the Sandbox environment, it did not show the promotional payment popup but returned a “restored” status.

However, when I tested it in the Xcode environment, it correctly displayed the payment popup, but after I tapped the Subscribe button, it showed an “Unable to Purchase” popup like this:

And in the console I could see this error:

Received error that does not have a corresponding StoreKit Error: Error Domain=AMSErrorDomain Code=305 "Server Error The server encountered an error" UserInfo={AMSURL=http://localhost:56862/WebObjects/MZBuy.woa/wa/inAppBuy, AMSDescription=Server Error, NSDebugDescription=Server Error The server encountered an error, AMSServerErrorCode=3903, AMSStatusCode=200, AMSServerPayload={
    "cancel-purchase-batch" = 1;
    dialog =     {
        defaultButton = ok;
        explanation = "Contact the developer for more information.\n\n[Environment: Xcode]";
        initialCheckboxValue = 1;
        "m-allowed" = 0;
        message = "Unable to Purchase";
        okButtonString = OK;
    };
    dsid = 17322632127;
    failureType = 3903;
    jingleAction = inAppBuy;
    jingleDocType = inAppSuccess;
    pings =     (
    );
}, AMSFailureReason=The server encountered an error}

Could someone help me resolve this issue? I’ve been struggling with it for two days and feeling exhausted...