I have a Nexus 5 and have a EC315 Huawei WIFI datacard. I used to connect my phone through Wifi and it used to work flawlessly. Recently I got a notification for updating to Lollipop 5.1 from 5.0.1 and I switched on the Wifi to download the software update, but the phone would connect and immediately drop the connection in 1 sec, this kept on happening. I checked with my laptop, it was connecting perfectly. Finally I got the firmware update through my office Wifi which also connected perfectly with my phone. I finally came across this thread and tried all the suggestions. I was not wanting to do a factory reset on my phone as it would entail the painful process of downloading all the apps. Finally I reset the wifi dongle to factory default and without any result. As I am writing this to you for your help, I happened to tinker with the user manual of the Huawei device, I came across FAQs which said that the mobile device's antivirus could interfere with the data services, so I immediately opened the McAfee app and disabled Wifi security and then tried connecting. Thankfully it connected and I got about to a workaround. Hope this helps.