iTunes in the Cloud - Cannot enable automatic downloads on iPad
If anyone else has a similar problem, you may find the following snippet useful.
My iPad 2 was not showing (on my Mac) as a device associated with my iTunes account . On closer investigation, I appeared to have trouble enabling the automatic download feature on the iPad using SettingsStore. Each button for Music, Books and Apps would switch off by themselves after a few seconds.
Simple fix is to Sign Out of your account on the iPad then sign back in. Buttons would then remain switched ON and the iPad correctly appeared as a device in the iTunes account on my Mac.