Sometimes the string may get stuck inside the end when you're trying to replace. This is usually due to the string or knot being too thin. It helps to use a needle, thumbtack, or end of a paperclip to poke out the remaining knot after cutting the string. If the knot keeps slipping out or getting stuck, also try tying a bigger knot.
Check that the batteries are installed correctly, and also check that they have charge. Be sure to slide the metal cap underneath the hooks with the spring touching the battery. If they still won't turn on, try to use a cotton ear stick to wipe off the metal contact point inside the tube of the LED as it may build up corrosion over time. If all this has failed, it might be time to get a new LED.
After paying, your order should come with a tracking number that will help locate its whereabouts in the shipping process. International orders outside of the USA usually take 2+ weeks to arrive.
Once shipped, it is mostly out of my control to make sure they go through the mail properly. If you have not received your order or they are taking a long time to arrive, please
contact me as there may have been an issue with shipping.