Skyconnect: device paired successfully, next day lost, now does not connect-pair anymore

Hi, I installed Skyconnect, paired 2 devices (2 Sonoff SNZB-02D)
very easily and fast. Everything worked fine

After some days I had to reboot the host, I did not pay attention, but now the 2 devices are offline. Tried to re-pair but nothing, so I deleted one of the devices, try to pair it again but it does not find it.

What shall I do?