Mi Desk Lamp won't reset

I bought a new router and I need to connect the Mijia Desk Lamp to the new WiFi.
However, I can’t reset the lamp. Strange as it sounds, if I press the reset button for 5 secs, the lamp just flashes one time and then turns off (the brightness goes to maximum, than it turns off). And then nothing happens, I just can turn it back on from the knob.

Is there any way to have an “hard” reset on this?

A few months ago this lamp had some problems when it wouldn’t turn on. I then tried replacing the power adapter with no results, until some day I tried to turn it on again and it worked, with no apparent reason at all.
Now it’s been working fine for some months, but I can’t change its connection settings

Thank you