Visual Studio 2015 Deployment Error DEP0600

I am running Visual Studio 2015 on Windows 10.
I wrote a simple Windows Phone 8.1 project (Hello World) in Visual Basic.
The program worked all right in the Emulator.
I attached my phone (Lumia 640) to my computer using the USB connection.
I clicked on Deploy and got the following error:
DEP0600 : The following unexpected error occurred during deployment:
Index (zero based) must be greater than or equal to zero and less than the size of the argument list. HelloWorld

Can anyone tell me how to get rid of this error, or what is this error telling me?

Thanks.

The problem was that I didn't register my phone.
OK now.