How do I unmute a contact? On my S6 with Android 6.0.1, one of the contacts in the default SMS app has a mute symbol (strike-through speaker) displayed next to the name. For this contact, new text messages don't trigger a notification. How do I change this? I've looked through all options in the message app and in the contact app and didn't find anything.
Had the same problem. Took me a bit to figure it out. 

Go to messages, tap on the thread for that contact, tap on their name in the top left corner, this will take you to conversation settings, turn notifications on.