connection of jio wifi in Android 5.1 version
Some sites recommend to restart the router device, and sometime it works.
Instead of every time restart the router to solve the Wi-Fi problem, it worked for me:

Inside the router configuration (e.g., accessing the IP 192.168.0.1), change the "Group key update" value from 0 to 30 seconds, under the "Wireless > Security" configuration, right below the WPA-PSK/WPA2-PSK item.

Router: TP-LINK TL-WR740N / TL-WR740ND.