It turns over but will not start

Welcome to the forum, I'd make sure the battery has a full charge and the connections are good. You can place digital voltmeter leads across the battery posts, have a helper turn the key to crank, note the voltage reading, shouldn't drop below 9 volts, some info says 10. Around here some of the national brand autostores will load test battery.

If you think there is an excessive drain on the battery with everything turned off. You can do an amp draw test. The usual spec is well below half amp. Different makes and models, the spec could be higher.