Step 1. To exclude issues caused by computer settings, we suggest restarting your computer and try it again.
Step 2. Please make sure you are using the latest HTC Sync Manager. (click "三" icon at the right upper corner in HTC Sync Manager screen > Check for updates)
Step 3. To exclude the possibility of conflicts from 3rd party applications, please try restarting your phone by press and hold the "POWER" button > choose "Restart" in Phone options pop up window.
Step 4. Plesae make sure "USB debugging" mode is turned on. (Slide the Notifications panel open, and then tap Settings > Developer options > USB debugging)
Step 5. Please make sure there is no obstructions between your USB cable and the USB port, and try a different USB cable with a different USB port.
Step 6. Please check if there is a "My HTC" device shown on your computer. (On your computer, right click on "Computer" icon > property > choose "Device manager" > Android USB Device) If you can't find "My HTC" on your computer, please uninstall the synchronize software from your PC then reinstall it again.
Step 7. If you could see your phone as the portable device on your PC, but there is still no "Android USB Device" in "Device manager", please try to manually update the driver
for your phone. (Expand "Portable Devices" in "Device Manager" > Right click on your phone's name or "MTP USB Device" > Update driver software > Select “Browse my computer for driver software” > Tap “Let me pick from a list of device drivers
on my computer” > Don’t check “Show the compatible hardware” > Select Standard USB main controller > Select USB composite device in the right hand side list as the screen shot below and then click Next > After you click Next, if there is Warning message window pop up, please choose Yes.