"Lock & Erase" feature on my android phone
The Android Device Manager is only able to work if: 

1 .You enabled it on your phone.
2. Your phone has an active connection to the internet.
3. At the time its connected to the internet, your google account is still signed into the phone. If your finder performs a hard reset on your phone or resets it to factory default settings, your google account is erased effectively rendering ring lock or erase useless.
Are you using a web browser to access the ring lock and erase feature?