Sonoff Pow Ring Flash?

Hi

Someone has succeeded to flash a Pow Ring from Sonoff with ESPHome ? I have tried multiple serial adapters but so far no luck using the 4 pins avalaible on board for flashing.
According at documentation I have to hold only button of the device while plugging in power/serial on it so ESP is in Flash mode but so far no communication :frowning:
I have done quite a lot of flashing in the past but first time I get no luck !
Something special with that device ?

Thanks

Vincèn