'06 Chevy Cobalt Won't Start

Maintenance/Repairs
2

Sounds like the battery cables were connected up backwards. Most likely situation based on what you posted. In that case, something gets damaged. Best case is a fuse or two blew. Worst case, a module failed. Start by checking fuses. Can you describe what it does do now? For example, do the dash lights illuminate as normal when attempting to start? Does it crank normally just not start? etc