The lights are bright enough and it is awesome not having to run wires and worry about overloading a circuit.
Most of the length of the string is from the solar panel to the first tube. In this section, there is a connector with 2 pins that aligns with 2 holes from the other section. If you disconnect make sure you reconnect the same way. If your lights don’t work try disconnecting and turning the connectors (changing which pin goes in which hole) , and reconnecting.
I hope these last through multiple years. And I wish I wanted to spend $2k on lights. Because I really think I need 8-10 strands in each tree.