Firmware Update Error On Airport Base Station 2

We don't know.......

Whether you are using a Mac, a PC, or an iPhone / iPad to try to update the firmware.

Whether you are connecting the Mac or PC using WiFi, or whether you have a wired Ethernet cable connection between the computer and the AirPort

Whether you have a 2nd Generation AirPort Express or a 2nd Generation AirPort Extreme

Can you help us with a bit more information?

Restart the Mac

Restart the AirPort Extreme

If possible, connect an Ethernet cable from your Mac to one of the three LAN <--> Ethernet ports on the AirPort and turn off the WiFi on the Mac. If your Mac does not have an Ethernet port, you need a Thunderbolt to Ethernet adaptor or USB-C to Ethernet adapter.

What firmware is it currently running?? You might need to take it in steps if you have not upgraded in years and years.

But it is amazing a Gen2 Extreme is still running.