Quick heads up: If your PC happens to download and install the latest major update of Windows 10 that was released this month (Build 1809), it might no longer detect your Netduino device in Visual Studio.
If this happens to you, try re-installing the Netduino SDK from the WildernessLabs download section.
Once you do that, your VS should detect your Netduino device again.
Additionally, if the Netduino Deploy tool doesnt detect your Netduino in BOOTLOADER mode, try re-installing the BOOTLOADER drivers too.
Hope this helps,