Can't restart my hub

This morning I have added my wifi id and password into hubitat. Then they ask me to reboot and since that my hub has never reboot. I have try to reboot, soft reset ... through the port 8081 but nothing work. When i do the soft reset i have a message : unknown error occured.
Please help, i dont have any idea what to do.
PS: i have a backup.

The hub doesn't have built-in wifi, which is used when you use an OTG adapter and plug a wifi dongle in the hub. Try pressing the little circle button on the bottom of the hub with a small pin. It should be near the edge and is the only circle hole on the bottom, the rest of the holes should be small squares.

I pressed on that button but it didn't do anything.

Could you please elaborate what are the symptoms of your problem? Additionally, please send me a private message with your hub's Hub ID or MAC address, so we can further investigate.