Why has romulation stopped working alternative site?

You're probably talking about the NDS games section being unavailiable for download, right? If so, it's because of legal reasons and how Romulation respects the requests of game owners. Most likely some of the owners sent messages saying they wish for Romulation to stop giving their games out for download, as many users just abuse it to get a free game or, in this case, ROM. They feel it is more harmful than helpful and as such it is now taken down and NDS downloads are permanently disabled.