Do you have any power at all - does the starter turn over but not start the engine, and do the headlamps work? If yes, the problem may also be a starter motor or solenoid or wire. If no, the problem could be battery cables, a defective new battery, or a short in another circuit or electrical item. See the following thread for one example of a similar problem.
Finding a voltage drain
Good luck, and let us know what works!
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