After updating to the recently released build #10041 of the Windows 10 Techincal Preview, I found that Windows Update wasn't working for me. The old style Windows Update was no longer available from the Control Panel. The new Windows Update in the modern "Settings" app showed that I had no updates available, and last checked for updates on 2/2/2015. If I clicked the Check Updates button, nothing seemed to happen, or occasionally the "last checked" date would flicker briefly, but not change.
This PC is a member of a domain, with an active System Center Configuration Manager 2012R2 server. As such, it would normally get it's updates from the SCCM server (which in turn pulls them through the associated WSUS server.) However, SCCM doesn't offer updates for the Technical Preview, so that isn't an option when running a preview build of Windows 10.
I found that to get Windows Update working, I had to change the policy setting which points my workstation to the configmgr server for updates. The easiest way to do this in a one-off situation like this is to edit the local policy.
Open the start menu, and type "gpedit.msc" and press enter. This should launch the Local Group Policy Editor. In the left pane, expand "Computer Configuration\Administrative Templates\Windows Components" and select the "Windows Update" folder. In the right pane, look for any settings with a State other than "Not configured". The important one here is "Specify intranet Microsoft update service location". If this setting is enabled, Windows will check the specified server for updates, instead of Microsoft's internet based update servers. Double click on this setting, and change it to Disabled. (This setting should automatically revert back to the previous setting after a period of time, but you may want to make a note of it before you make the change, just to be safe.)
After disabling this setting, apply the changes and click ok. Wait a moment or two, then open the modern "Settings" app again. Select "Update & Recovery", and click the "Check for Updates" button. The "last checked" info should disappear, and be replaced with a message that it is checking for updates. After a few minutes, some updates should be available. (I believe to date there have been 4 windows updates released for build 10041. In my case, I also had a few driver updates available which had been released in the past week or so.)
This change will also allow the computer to check for new builds of the Windows 10 Technical preview, including the just released build 10049.