In recent factory firmwares Ubiquiti prevents any installation of third Party firmwares by using signed firmwares. any unsigned firmware cannot be installed. since it is not possible to downgrade this firmware to a previous version which did not go that idiot move it is required to use a special flashing method. simply copy flash-upgrade.bin with scp/winscp to your ubiquiti device into the /tmp directory. login with ssh to your ubiquiti device and execute the following lines chmod 700 /tmp/flash-upgrade.bin /tmp/flash-upgrade.bin the router will now flash itself. once ths command has finished, simply powercycle your device. future upgrades can be done with standard dd-wrt webgui. to get back to ubiquiti firmware, you have to use the tftp recovery method