In the first post, you said that the fan was still running, but now there is no power at all?
Do you have a solar sunroof? I don't know when that option was available but it would probably continue to operate your fans regardless of the battery.
If it was a problem limited to the starter, all your other accessories should still function from battery power. The fact that
nothing works seems to indicate a problem at the source. It really sounds to me like either the battery is shot or a bad connection.
If the battery, its connections, and all points in-between check out, then I guess the next thing to look at would be the ignition switch. But since the car was sitting for a while I would put that low on the list of suspects and check over the other stuff I mentioned one more time.
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2001 S8 - Racing Green Pearl Effect