There are multiple reasons that may cause your MacBook won't turn on, such as drained battery, faulty charging, display issues, startup disk corruption, etc.
You can fix your MacBook won't turn on with the following methods:
- Charge your MacBook for a longer time. Charging your MacBook for a short time won't let it have enough power to turn on.
- Check the power connection. Check whether you plug the power cable correctly and change a port to plug the power adapter. Change your power cable to a new one in case it is corrupted.
- Disconnect all external devices. Bad contacts, short circuits, or consuming an unusual amount of energy might prevent your MacBook to turn on.
- Reset SMC. Check the System Management Controller that controls the entire MacBook power-on process. Your MacBook won't turn on if the SMC has failed to receive power or assign a power supply to the hardware circuit.
- Run a power cycle. If your MacBook is Intel-based, you can take this way to force cut the power to it and then force restart your MacBook.
- Check your display. Check whether you turn down the brightness to the lowest.
- Send your MacBook to get repair services. You mentioned you send your MacBook to the authorized service provider and they said the problem is with the main logic board and battery. You can take the below ways first to check whether they can help you to turn your MacBook on. If not, you need to send it to the Apple Store to get professional suggestions.