computer not communicating

I have a 1999 Plymouth Breeze and the computer is not communicating with the reader; what is the possible cause? My mechanics are stumped. There are a lot of things that can pull a network down. Not really a lot of info to go off of here. It could be some thing as simple as a blown fuse that powers the DLC not letting the reader/scanner power up....

It would help to know what kind of equipment you are using & exactly what type of error you are getting........
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