I am having the same issue of lights not working as many others. I purchased a pre-strung 9’ tree in 2015. Cost was approximately $1000. A couple of years ago multiple strands of lights stopped working. Balsam Hill sent me replacement lights. I re-strung the lights (a very tedious and time consuming job). Three more strands went out again (in 2021). By the looks of all of the bulbs on a strand, the wiring must be faulty and is shorting out. Very poor value for the price paid, very limited warranty period, and no customer service in the way of repairs. I would not recommend.