2006 colbalt

There's a fuse that can be blown which prevents the code reader from connecting with the car. Happened to mine. Years ago now, but I believe the fuse was in the fuse box under the hood. Start by checking that. When you say nothing happens, do you mean it won't start, or it won't even turn over. If it won't turn over I'd start checking the battery, electrical connections etc. If it won't start I'd listen to see if you can hear the fuel pump working and check if you've got fuel pressure. Could be lots of other things too, but that's a good place to start. At least you're scanning for codes first. Most people who come on here spend a few hundred dollars on unneeded parts first and then do the diagnostics.