A good number of people who own the Samsung Galaxy S8 and Galaxy S8+ Plus have reported some issues with the side power button. It is understood from the claims that when you press the power button to wake your smartphone, there is no response.
Although the power button lights up the screen, the screen does not turn on the display when you press the power button. You may also encounter the same problem when you receive an incoming call. During an incoming call, your Galaxy S8 will ring as normal but your screen stays black and does not respond.
In some cases, some of the apps you install on your smartphone might result to the power button problems. It is recommended to enter your smartphone into a Safe Mode (Learn how to get your Galaxy S8 smartphone into and out of the Safe Mode) Once you have your phone entered into the Safe Mode, you can test to see if the button is functional. Currently, there is no known malware or application that may cause the power button to fail, however, the Safe Mode is a perfect way of discovering if the problem is caused by a rogue app.
Alternatively, you could opt to reset your Galaxy S8 or Galaxy S8+ Plus to return it to its factory setting especially if you note that the problems persists even after testing it in the Safe Mode. If you reset your Galaxy S8 make sure that it runs the updated software as provided by your service provider. I would recommend that you consult your service to get the latest information about the latest version of the system update for your Galaxy S8 or Galaxy S8+ Plus.