How can I get Helium to work on my One? I'm trying to backup apps on my OnePlus One using Helium.

When I open the Helium Windows Desktop application, it works some magic and tells me Helium is now activated on my phone, but the app still shows a spinner and says it's waiting to be activated.
As noted in the thread [How to] Helium Backup by Bassick, one should use the Helium Chrome app to activate Helium. Then it will works just fine.