The Ubiquiti reset button’s function is based on how long it’s depressed when the node is already powered-on:
Hold for 5 seconds for a password reset and DHCP server reset.
Hold for 15 seconds and the node will return to “just-flashed” condition.
(NOCALL-xxx-xxx-xxx)
Hold for 60 seconds to put node in tftp mode.
(You can also hold the reset button while applying power to the node)
If the reset button on the node is not working you can use the reset button that is on some of the Ubiquiti POE injector.