Review on Homemory 10pcs Submersible LED Lights with Remote Control - Waterproof EFX Lights for Vases, Showers - Battery Operated Color Changing Underwater Lights for Easter, Halloween by Jami Boetel

In my package 3 out of 10 didn't work. The problem was that the bottom contact wasn't sticking. Some users say to tighten it (which works in some cases but didn't work for me). To fix it, I took out the batteries and, using a cell phone tool, gently pry up the bottom (+) contact so it bent up without tearing the metal. Then I put the batteries back in and screwed them in fine. The circuit is closed, the light is on. Disclaimer: This may affect your warranty. On the other hand, the "Contact us for help" information has been redacted in shipping, so it seems this issue is quite common.