It seems that either the USB hub or the USD devices causing the Mac not to boot up. You can troubleshoot the issue from these involved parts such as changing a USB hub, disconnecting peripherals, etc.
If the Mac won't turn on when the USB hub is plugged in, then it may be the faulty accessories that block the Mac's power-on process. To find out whether it is the USB hub or connected USB devices that make your MacBook Pro unbootable, you can follow the steps below:
Ensure the USB hub is working. If the USB hub is defective, then it may affect the startup process of the Mac. To know whether the USB hub is problematic or not, you can connect another healthy USB hub. If the MacBook remains unbootable, then the culprit is not the USB hub.
Disconnect all USB devices and reconnect them one by one. If you have connected several USB devices to your Mac via the USB hub, any malfunctioned USB device among them could be the culprit of an unbootable Mac. Therefore, you should first disconnect all of them, and reconnect one each time until you find the defective one.
If the Mac won't turn on when no USB devices are connected, you can try the methods below:
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