It happened when during the process of updating the firmware of RocketM, NanoBeam, NanoStation and other Ubiquiti devices power was lost, or there were some other problems after which the device could not be accessed via the web interface and it did not work.
I will describe in points how you can restore the firmware:
1) Download firmware from the official site https://www.ubnt.com/download/, which you need to flash the device.
2) Start TFTP server. I described the launch example in these articles:
Starting a TFTP server in Windows
Installing and Configuring a TFTP Server in Ubuntu.
3) It is imperative to assign the computer exactly this IP address 192.168.1.254 and the subnet mask 255.255.255.0.
4) Turn off the device in which you need to restore the firmware, with the device turned off, press the RESET button and hold it to turn on the power to the device, continue to hold the RESET for 8-10 seconds, and then lower it. With these manipulations, we activate the recovery mode and the LED indicators will flash alternately. The IP address of the device 192.168.1.20 should start pinging, if not pinging, then alas will not be able to recover. To check the ping, the command is executed on the command line:
5) Now we’ll upload the previously downloaded firmware file to the TFTP server directory and send it. From windows, this can be done with the command:
tftp -i 192.168.1.20 put XM-v5.5.4.build16501.bin
From Linux, this is done by commands (you may have to put the firmware file in the user’s home directory):
tftp connect 192.168.1.20 bin trace put XM-v5.5.4.build16501.bin exit
When the firmware file from the TFTP server is sent to the device, you must wait until the firmware update process occurs and the device automatically reboots.