You can enable LLDP-MED on OBI302 by doing this on the web interface of the OBI302.
Would you try this procedure?
In the system web interface, go to Admin Settings > Network > LAN Properties.
Select the check box at Enable LLDP and click Save.
You can also auto provision our ATA by going to your web portal. Please go to Phone System > Phones and Devices > Phone Number for your ATA > Change phone > Existing Phone > Polycom OBI302.
Please let me know if you have further questions!