Wifi beacon missing after firmware upgrade

I received the Maix Dock with factory firmware MicroPython v0.4.0-87-g42e92b235-dirty on 2019-11-07; Sipeed_M1 with kendryte-k210, when the board was powered on it will show ESP_4xxx in the list and I could connect to it and do a PING from the connected to the ESP access point

I downloaded maixpy_v0.5.0_12_g284ce83.bin and flashed the board,

Now the version is MicroPython v0.5.0-12-g284ce83 on 2019-12-31; Sipeed_M1 with kendryte-k210

However the Wifi beacon is no longer appearing on Wifi scans. How to get it back?

@Zepan