android 5.X/6.X exclamation mark with the Wifi & celluar image
The issue is caused by the Android 5.1 bug and there are two methods to solve the issue.
Download the apk and change it to androidcheck.kiritostudio.com
Use the following command via adb(You can find the slim version of adb here):
settings put global captive_portal_server androidcheck.kiritostudio.com
After finishing setting, suggest to reboot the device and everything will be ok.