Sorry to hear that. In these cases it’s usually due to a faulty connection to an SD card or improper data on the SD card. As the card was pre-loaded (may be worth checking that it’s suitable for the Pi 3 B+) that’s likely not the issue, I’d recommend checking that the connection to the Pi is clear and to give the whole thing a thorough cleaning. All the best with your Pi! Make sure to let us know if there’s anything else we can do to help!