However, many Galaxy S8 users are complaining that the dedicated Bixby button does not respond to their tap. When pressing the Bixby button, nothing will happen. It launches neither the Bixby personal assistant nor the Bixby home page. If you are experiencing this issue, there is a simple solution to fix it.

How to fix Galaxy S8’s Bixby button not working issue: Thanks to a Reddit user, instead of long pressing the Bixby button, pressing the button very quickly will launch Bixby. Many users confirmed this working. It seems that this is neither a hardware issue nor a software issue. Samsung has assigned Bixby button not just to launch the Bixby assistant. The button has some other functions as well. According to the Reddit thread, a quick press of the Bixby button is assigned to launch Bixby assistant and a long press probably for voice command feature, but Bixby voice is not released yet. (Source)