This is a known issue that may occur when you first install build 9926 of Windows 10 Technical Preview. You may find a fix for the issue by checking for Windows Updates. To do this without the Start menu:
If none of these solutions are working, please check that your User Account Controls are set to the default recommended settings.You can find this control by going to Settings and searching for “User Account Control”.
Once the control page opens, set it to “Notify me only when apps try to make changes to my computer” and click
Also, make sure you’re using an administrator account, and that you are not on a child, guest or standard user account when attempting these solution steps.To check this, go to Settings > Accounts >
Other user accounts.This will list all the active users and whether they have administrator privileges.
If you’re current account is not an administrator account, you’ll need to sign out and then sign into one of the existing administrator accounts listed.From there, go back to this page, click the entry for the account you were using, click
Edit, and then switch the account to Administrator.