Car doesn't start

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My front lights light low. I jump started it and run the engine for 30 min but when i turn it off and start it again, it doesn't want to go through again. There 's no indication in my dashboard that my battery is dead. My battery is barely 3 years old. First time to encounter this. I never left my lights on and it happened only suddenly when I tried to restart it again after just 2 minutes of turning it off. Turning the key on only lights up my dashboard and cranks continuously but it doesn't start at all.