I have several of the Blue 2-1 switches, and I recently switched my coordinator, and had to re-pair all of my devices. But about half of my Blue switches won’t take the button combo for factory resetting. Half of them worked fine, the others I can’t get to accept any kind of configuration command (it won’t change the LED bar status for switch on/off, trying to configure as single pole/smart switch mode/dimmer/etc don’t give any feedback, factory reset never shows the green/yellow/red color cycle). I’ve been able to get the other half of the switches reset and working properly, so I definitely know how to do it right.
It also persists through pulling the safety disconnect. I’ve had them do this before when I was having some mesh issues, but when I just let them sit for an hour or two, it completely went back to normal. But now it’s been days, and these are the only devices I haven’t been able to re-pair to the mesh.