Developer failed to unlock Windows Phone 8 device

I want to test my app on a Windows Phone 8. But in order to deploy any app to the device, we need the developer to unlock it. I tried to do it with Visual Studio 2013. But when I try to do it -

I am getting 2 errors - 1. Check the date and time. It doesn't match

2. Check your Microsoft credentials and try again.

Please, help. Have tried a lot. Thank you in advance