I can't find anything in the manual that describes the nature of the FAULT message. In fact, it's not mentioned at all. If the unit detects a fault at its output, I would expect a bit more information. This unit does a programmable level of input error protection, too, usually set at 100%. Still, there is no indication in the manual whether an input issue would be described as a fault; that usually means a short or lifted ground at the output.
Is that a fault code that you can decipher in the manual, or just a light telling you nothing but your UPS is dead?