Never use Helium. Asking for the dev's help is like taking blood from a stone and even when they finally decide to help you, they give you very little to work from. Here's the reason why I can't restore my Nexus, according to the dev:
Directly from our wiki: Helium ceases to recognize backups
There are a few reasons for this, listed below;
You manually moved the Carbon backup folder that is located at the root of your device storage. The app stops recognizing backups that are manually moved, as it's an unsupported scenario. There is no workaround or fix for your issue as it is unsupported. In the future, make backups to your PC using the PC Download feature. To backup to your PC, use the PC Download feature found in the settings menu of the app on your device. This will launch a server that you can connect to via a browser on your PC provided that your PC and device are on the same network that you own or control. Upon launching the server, it will give you an IP address that you put into the address bar of the browser on your PC.
You copied and pasted the folder, your backups will cease to be recognized.
Posted via my Z10 using Android Central App