I have a FSP1004 panel with the “Anunn trouble” light lit. There is and never has been any peripheral modules connected. A pull station was maliciously activated. After my tech came out to reset the pull and panel is when this issue started. Power cycling did not not correct the problem. We did not try reprogramming the panel.
I’m not sure what the issue is, but I would start with figuring out how to make sure the panel is not programmed to have an annunciator. Something weird could have changed with the programming.