Cannot switch to Start Screen by Left-click of Start-Memu

Question

I've installed W10 TP Build 9926 onto W7 Ultimate 64-bit.
It works almost fine, except inability of Left clicking on Start-Menu. The Left-click has no effect, or my screen does't change to Start screen.
The Right-click works, i.e. context menu appears. 
<brief environment> dual monitors, latest display driver by Nvidia.... Are there any further information needed?  
Thank you.

Answer 1

I've installed W10 TP Build 9926 onto W7 Ultimate 64-bit.
It works almost fine, except inability of Left clicking on Start-Menu. The Left-click has no effect, or my screen does't change to Start screen.
The Right-click works, i.e. context menu appears. 
<brief environment> dual monitors, latest display driver by Nvidia.... Are there any further information needed?  
Thank you.
It is possible an Windows Update is needed, namely KB3036140.
Since you cannot use Start Menu, lease follow this instruction given by Insider Hub......
Checking for updates may fix this problem. To check for updates without the Start menu, do the following:
Select the Internet Explorer icon.
Type http://update.microsoft.com into the address bar and select
Enter.
If you are prompted to run a control, click
Yes.
This should bring up the Check for updates window. Install updates.
If no update is available, or the available updates don’t fix the issue, restart the device–this should make the Start menu appear. To reboot without using the Start menu:
Hold down the Windows key and select L to lock the device. Swipe up or select
Enter to open the sign in screen. Select the
Power icon on the log in screen to restart the computer.            
OR
Hold down the Windows key and select R to bring up a command prompt. In the prompt, type
shutdown –r to restart
Good luck.