Hi Ktruong,
You have to upgrade to 10.xx, as per: https://gtacknowledge.extremenetworks.com/articles/Q_A/What-Firmware-is-needed-to-support-AP3935-AP3965-Access-Points/
Support for more recent APs (like 3912+3916, 3915+3917+3912) has been introduced with more recent releases of the firmware than 10.01.
Hope that helps,
Tomasz