How to reset Ubiquiti Dream machine to factory default

Hello team, When we reset factory. do it return the first OS?

How do you reset it if its not adopted?

UDM Pro was stuck in a boot sequence. In the end I saw an error message in the LCD screen to perform a factory reset. However, when I try to do this with a paperclip, nothing happens. Tried removing the power cable and reset again, as well to reset during the boot sequence. Nothing happens.

That is a Pro. It is a different machine than the DM.