Last night, Windows Insiders who installed the leaked Windows 10 Build 10056 were notified about the availability of Windows 10 Build 10061 in Windows Update. But when they click install, the above error message was displayed. Gabriel from Windows team today confirmed that only Microsoft employees will be able to install Windows 10 Build 10061.
@CrazyCatsGot2 People who installed the leaked 10056 build will see 10061 offered, but unless they are MS employees it won’t install.
— Gabriel Aul (@GabeAul) April 15, 2015
This is one of the disadvantage of installing leaked builds. There won’t be clear upgrade paths forcing users to install fresh OS from ISOs.