Try the steps below if your watch does not display the connection screen, does not appear as a drive in Windows, or appears as an "unknown device" in the Windows Device Manager.
Try a Different USB Cable
Try a Garmin branded cable, if available.
If a new cable must be purchased, ensure that the cable is a USB Data Cable and not a USB Charging Cable.

Ensure That the USB Port is Working Properly
Try a different USB port on your computer and/or test the USB port with a different USB device.
Avoid connecting through a USB hub, USB extension cable, keyboard, or monitor.
On desktop computers, use the USB ports on the back of your computer.
- Avoid using a PowerShare USB port.
- Contact your computer manufacturer if you are unsure whether your computer uses PowerShare ports.
Laptop

Desktop

Disable USB Selective Suspend
USB Selective Suspend will limit power to connected USB devices, including your Garmin device. It can potentially cause recognition problems.
Disabling USB Selective Suspend
Unplug your watch from the computer.
On the computer, open Control Panel.
Ensure View by is set to Category.

Select Hardware and Sound.

Select Power Options.

Select Change Plan Settings next to the currently selected power plan.

Select Change Advanced Power Settings.

Expand USB settings.

Expand USB selective suspend settings.

Select Settings
Select Disabled from the drop-down menu.
Select OK.

Plug your watch back into the computer.
Restart the Computer and Try Again
Plug the watch into the computer before restarting.