Well, the problem relates to the wireless network. To fix it we suggest to set a static IP address for that particular Wi-Fi address. It means that you have to know an available address on the LAN, the gateway address, and the DNS addresses (DNS1 и DNS2) for the network. As for the latter you can use Google's default DNS addresses of 18.104.22.168 and 22.214.171.124. We do not claim that this way is the best one. Nevertheless it works!
How to solve Wi-Fi exclamation point?
- Go to "Settings" on your Android. Select "Wi-Fi";
- Find the network in question, long-press its name. You will see the pop-up menu, select "Modify network";
- At the bottom of the screen select "Advanced options", then "IP Settings", then "Static";
- Enter the necessary network information in the available boxes and tap "Save". As soon as you are done, restart your device. After restart complete, look at the notification panel to make sure you have connected the same network and without the exclamation point.
It is possible you will repeat these steps more than once. You may want to do so for all wireless networks you employ. Usually upgrade OS to Android Marshmallow solves the issue once and for all. Thus far, the static IP-address will secure your device from the exclamation point.