I managed to make it work. Make sure you connect to 2.4ghz wifi on your iphone. At first, i connect to 5ghz wifi. However, since my series 5 only have 2.4ghz, then it cannot connect to my router as my iphone is connected to 5ghz. Hence, once i changed my iphone wifi to 2.4ghz, walla, the apple watch managed to get connected to find the update. hopefully this will help others.