Windows 10 has a strange default setting regarding speakers and headphones. In prior Windows iterations, when plugging a set of headphones into a laptop, the sound automatically switches to the headphones from the speakers.
In the current Windows 10 iteration, when plugging in headphones, the little speaker icon will show that the output is selected for headphones, but the sound will still be coming out of the speakers. Then you have to switch to the speaker icon, and back to the headphone icon to get the headphones to work. This is the case for when you are already playing sound, but when you are not actively playing a sound, the speaker / headphone switch will automatically happen.
It turns out there is a change under Control Panel / Sound. You’ll have to go through each speaker and each headphone entry in the list and make this change. So for instance:
Control Panel >> Sound >> Headphones >> Properties >> Advanced: Turn off “Allow application to take exclusive control of this device”
Do this for CP >> Sound >> Speakers and all CP >> Sound >> Headphones
Now Windows will allow the switch between speakers and headphones to work automatically. This also allows multiple sounds to happen at the same time, so a facebook ding won’t interrupt a youtube video, which was also annoying as heck!