Airport express showing solid amber light
Unfortunately, this can mean one of two things:
1) The Express is locked up and will need a Factory Default Reset procedure to try to return the device back to its original default settings so that it can be reconfigured again.
2) The Express is defective. If you cannot get the Express back to a slow, blinking amber light after a Factory Default Reset, the Express will need to be replaced.
Try the Factory Default Reset a few times and report back on your progress.