No more wifi at all from drone!

In FreeFlight 6 / Parameter / Network / Wi-Fi band, being connected to ANAFI, I simply went from “AUTO” to “MANUAL” and chose a channel in the 5Ghz band: So I instantly lost the connection with ANAFI.
But now, ANAFI no longer broadcasts any network SSID, neither in 2.4 nor in 5 Ghz.
In order to “reset the config”, I pressed ON / OFF for more than 8 seconds, the 4 red LEDs on the battery were activated, but no “.txt” file appears at the root AND ANAFI still no longer broadcasts any SSID.

What is the model of the phone you are using ? Does it support the 5GHz frequency ?