Windows Phone 8.1 GDR2 no longer prevents Windows 10 for Phones preview from loading
Late last month, Microsoft announced that it had expanded the list of Windows Phone models that can handle the Windows 10 for Phones Technical Preview. The list included even the most basic of Windows Phone models, the Nokia Lumia 530. To no one's surprise, the list includes models like the Nokia Lumia 1520 and the Nokia Lumia Icon.
The latest Technical Preview for Windows 10 for Phones was sent out on Friday, and requires that the phones not supported by the first Technical Preview to load Windows Phone 8.1 GDR2. Unfortunately, the latter triggered some sort of problem on Microsoft's end that prevented certain models from moving on to Windows 10 for Phones.
Aul has given the "all clear" sign, so those who were affected should try again to load up the latest Windows 10 for Phones Technical Preview.
source: @GabeAul via WindowsCentral