When I control the device with Alexa, No "OK" response is heard and no error is prompted, only the indicator is off after a buzz sound.
This may be because Alexa does not precisely recognize the command and fails to parse the user's intention.
You are advised to change the device name in the app to one which is easier to recognize by Alexa, such as "bedroom light" and "bedroom light". Then, re-find the device and control the device with the new name. If the problem persists, please offer your device ID and app account for us to check the problem.