La carga de tvm anónima de Amazon s3 solo funciona en el simulador

I am using amazon s3 for my data storage and am setting a anonymous vending machine token (tvm) for upload via the app. Everything seems to work fine when I am using the simulator. However as soon as I switched to the actual device, the response from the getToken method of the AmazonTVMClient object was not successful. It returns code 408 with a message "Timestamp is not valid"

I cannot figure out why that it works on the simulator but not on the device. I have seen another post mentioned that it could be related to upper/lower case issue. But I doubted that it's the case.

Basically it will do anonymousRegister just fine but unable to get the token.

Se agradecerá cualquier ayuda. Gracias.