Question about Value RJ45 T-adapter

Unfortunately, it didn't work for me. No idea why. Unfortunately, only one of two connections works. Reconnecting is not the idea. Only one device works at a time. I have a network socket with one connection in the basement and wanted to connect two devices, but only one connection. Any ideas? House with network distribution cabinet and switch. A 2-socket on each floor except in the basement. Hence the splitter.