On my Glowforge Pro, what's that round thing above the power switch?

[dwardio]

It’s the Safety Interlock mentioned in this thread:

Pls help! Safety interlock open error msg on pro

I keep getting the safety interlock is open on my brand new pro. I tried turning it off, making sure all the connections (power supply) were plugged in all the way and secure. Rebooted over 10 times and it didn’t work. I carefully removed the print head, detached the cable and checked the pins none are bent or broken.