Still no answer ?
Request a callback from google play support. Apparently they can reset your device activation limit for you.
Step 1: Head to the Google Play support page, click Contact Us in the upper right corner, and then choose Music.
Step 2: Click "Problem playing music," then "Request a Call."
Step 3: Complete the call-request page by providing your phone number and description of the issue. (It doesn't matter if you're not a Google Play Music subscriber. I'm not.) Finally, click Call Me.