L6599 LLC resonant converter start up issue

[LChun.1]

1. Apply 15V at Vcc pin
2. Apply 50V at top of potential divider formed by 6M6 and 180k ohm at LINE pin

in order to get LINE pin voltage >1.23V

However, High side LLC mosfet (connected to HVG pin, on resistance: 47ohm, off resistance 10ohm)

GS pin is shorted with near 50ohm (mosfet gs pin damage) after step 1 and 2.

Please help to provide cause and solution.