Steve-
It appears your model is somewhat different than mine. My Magnum Energy, Inc., MS Series Inverter/Charger has a "Fault" lamp that lights, with no beep I've ever heard. The unit goes to Fault mode to protect itself, appliances, and batteries when normal operating parameters are transgressed, such as low batteries, high batteries, AC or DC overload, or excessive inverter heat.
I would heed the posts from others re. resetting your unit. You might do an online search for your brand and model of inverter/charger, and try to obtain an owner's manual for it by mail or download and print a pdf of it. The manufacturer may offer other assistance by email or phone as well.
Joel