I have a similar problem. My S-8 isn't connecting regularly to my home wifi. it works everywhere else - no problem.
At home I connect sometimes and other times I get the exclammation point. It doesn't disconnect once connected. i can leave home for 10 minutes and come back and then my phone won't connect.
I have tried all of the tricks noted in the forum. I have contacted my ISP and they say that everything is working correctly. All other cell phones in our home (iphones) all connect without a problem.
This all did start when we got a new router from Century link in the late spring. I'm not sure if there is a phone setting I need to change or what-- very frustrating.