There is a known issue in Windows Insider Preview build 10074 (see here).
- Developers cannot enable Developer Mode in the Settings app for installing and testing apps on this build. We'll enable this on an upcoming build. In the meantime, you'll need enable your device for development using the Group Policy Editor.
The current work around is enabling developer mode via Group Policy Editor or Register editor.
How to enable your device for development using the Group Policy Editor
If you use Visual Studio in a Windows desktop and you open a solution for a Windows 8.1 or Windows apps, you'll be Prompted to enable your device with this dialog. (You also need your device to is enabled to use the designers and debug your app.)
When you see this dialog, click OK. Then follow the steps below-to-enable your desktop from Windows insider Preview.
For Windows Ten Desktop
Use Gpedit.msc to set the group policies to enable your device, unless you have Windows insider Preview Home Edition. If you do has Home Edition, you need to use Regedit or PowerShell commands to set the registry keys directly to enable Yo ur device.
Use GPEdit to enable your device
- Open a CMD prompt with administrator privileges.
- Run gpedit.msc.
- Go to Local computer Policy > Computer Configuration > Administrative Templates > Windows components > APP Package Deployment
- Edit the policies to enable the following:
- Allow all trusted apps to install (Enables your device for sideloading apps)
- allows development of Windows Store apps and installing them from an integrated development environment (IDE) (Enables your device for development from Visual Studio)
- Reboot your machine.
Troubleshoot:enable Developer Mode in Windows insider Preview Build 10074