Nexus 4, Lollipop 5.1 WiFi Issue My Nexus 4 device stopped connecting to the Cisco router at work for some reason.  I thought it was because the upgrade to lollipop 5.0 (had Kit-Kat before) but I'm not so sure anymore.

I tried:


Restart the device
Restart the device with safe mode
Restart the router
Change the device WiFi frequency settings
Use static IP at the advance WiFi connection configuration
Forget the router AP and reconnect
Factory reset trough the device settings, recovery mode and complete flashing the Android Lollipop 5.1 factory image.


After factory reset I had the connection possible until restarting the device.
I checked with/without signing in, nothing new installed, didn't visit the store, just super clean phone - I could connect the network. after restarting the phone I can no longer connect which means it's not an application issue.

Some facts:  


I can connect other Cisco routers at work
Another Nexus 4 after factory reset connects with no trouble


About the device:


Nexus 4
Lollipop 5.1
build number LMY470
kernel version 3.4.0-perf-gf75bb4f


Any suggestion will be welcome, please let me know if I can provide more details.
Some sites recommend to restart the router device, and sometime it works.
Instead of every time restart the router to solve this Android 5.1 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.

My router model is: TP-LINK TL-WR740N / TL-WR740ND.