Follow these steps to check USB connections to the arm board (located inside the tower on the lower left wall)
Check that assembly related cables are connected. If any connection is corrected at any point, restart the system.
Check the USB Cable connection to the CPU.
If the error persists, remove the front cover, turn power on to the system and check the status lights:
If all lights 3x Orange LEDs are on, check if the USB cable is connected to the arm board
If NO lights are on, check if Cable 15 is connected to the arm board and 12V distribution board