iOS App Data Transfer

I made an app with reference to your source code. Now the app can connect with the IoT module. So when they got connected, it stops blinking the blue light. And I checked with the System Settings on my phone, it says IoT-DK-SFL is connected.

However, data transfer is not taking place. I send the configCommand when my page got loaded.

SensorController.shared().sendConfigCommand(UInt8(DIALOG_WEARABLES_COMMAND_CONFIGURATION_START))

I write a print line command in the writeValue function in SensorController.m checking what the result from the module will be.

- (void) writeValue:(CBUUID*)serviceUUID characteristicUUID:(CBUUID*)characteristicUUID data:(NSData *)data andResponseType:(CBCharacteristicWriteType)responseType {
CBService *service = [self findServiceWithUUID:serviceUUID];
NSLog(@"THe result for service is: %@", service);
if (!service) {
NSLog(@"Could not find service with UUID %@", serviceUUID.UUIDString);
return;
}

The result I got is null, suggesting nothing is received from the module.

2018-03-01 13:09:46.385908+0800 testing2[8690:4104855] THe result for service is: (null)
2018-03-01 13:09:46.386004+0800 testing2[8690:4104855] Could not find service with UUID 2EA78970-7D44-44BB-B097-26183F402400

Anyway I can fix this?
I attached my code.