If your windows 10 start menu does not appear when you select it, try these fixes:
Option 1

1. Start task manager
2. File > Run New Task
3. Type in powershell
4. sfc /scannow into the window and press the [Return] key
5. The scan may take some time and will end with one of three results.
   1. Windows did not find any integrity violations and Windows Resource Protection found corrupt files and repaired them mean there are now no corrupt files, but Windows Resource Protection found corrupt files but was unable to fix some (or all) of them indicates a problem.
   2. In this latter case, type (or copy and paste) DISM /Online /Cleanup-Image /RestoreHealth into the PowerShell window and press the [Return] key. This will download files from Windows Update to replace the corrupt ones and, again, this may take some time.

If this does not work, advanced options here: http://home.bt.com/tech-gadgets/computing/has-your-windows-10-start-menu-stopped-working-here-are-four-ways-to-fix-it-11364000314532