When charging it is best practice to plug the charger into the balance board first, and then plug the charger into the wall. And when finished charging unplug the charger from the wall first, and then unplug it from the balance board. This will stop the sparking seen when plugging the charger into the board. That sparking will eventually ruin the charger port or charger plug if the charger is not connected the way described above. However connecting the battery charger plugs in the wrong order will not damage anything other than the port or plug and will not damage the charger or battery.
Without troubleshooting the balance board it not possible to know with certainty which part is not working. We sell a lot of charger ports, battery chargers, and batteries so it could be any of these parts. The only way to know for certain would be to test the battery pack Voltage with a multimeter to see if it is discharged, test the Voltage at the charger port to make sure it is making contact with the battery pack, and to test the battery charger plug to make sure that it is outputting the correct Voltage.
Since you are getting a spark when plugging the charger into the balance board that points towards the charger port working. And since you are getting a green light on the chargers that points towards the chargers working. There is a good chance that the charger and charger port are good and the battery is fully charged, however there is problem with the balance board which is causing it not to work. Testing would be the only way to conform this though. If the battery pack has around 42 Volts in it then it is fully charged and the problem is most like with another part other than the charger, charger port, or battery.