Downgrade firmware for Shelly 1L

I updated the shelly 1L for the last firmware and then, the Shelly is not working, I can access to their IP address and I can hear the switch sound, but the shelly is not switching. How I can downgrade the shelly please to check if the update is the problem?.

Thanks,

Jose

Its necessary to go to http://archive.shelly-tools.de/ an follow the instructions.