Windows 8 sign in error code: 0x80070426
Solution 1:
I had this same issue and just solved it now. Go to Windows services (Win+R) then type 'services.msc'. Look for 'Microsoft Account sign-in assistant' and check if it is activated or not. If it isn't started, double click it and then set it to start up automatically. Restart the computer and see if it works - did for me. Hope this is useful!