When something won't work, it is very difficult not to get frustrated, I find, which does not help. Frustration clogs up the mind; you can't think straight; your mind gets stuck down a tramlines. So, the idea of this thread is to think of a checklist of practices to get things fixed quicker. Have you worked on that system recently? Whereabouts? You might have broken something while fixing something else. Look for loose wires or cables. Try to isolate the problem. Actually read the error messages What else? There must be lots?