I'm trying to turn on automatic downloads, but I see an alert that says 'This device is already associated with an apple ID.'

I recently bought a new ipod 4 gen 32 G. I had an 8 g .I'm trying to turn on automatic downloads so when I buy a song from Itunes it automatically downloads without plugging it into computer to sync. When I turn on Auto Downloads, It say...This device is already Associated with an apple ID You can auto-download purchases on this device with just one Apple ID every 90 days. You cannot associate this device with a different Apple ID for 30 days. When I click OK it turns th downloads off..Can someone help me? I've returned the 8g to regular factory settings as I'm giving it to a friend.