Hey guys I just figured out by myself what causes this annoying "google play no conncetion" on my google nexus 5!
It has something to do with the "ad blocker" app I installed way back and uninstalled recently. As for unrooted devices the app need to set up a proxy (long pressing the connected network ==> modify network ==> show advanced option ==> proxy) for its function. As such when the app is uninstalled, the proxy setting is still being remembered by the phone, and that causes the problem.
Simply delete the proxy settings on the selected network (aka don't use proxy), and it will work out.
It has something to do with the "ad blocker" app I installed way back and uninstalled recently. As for unrooted devices the app need to set up a proxy (long pressing the connected network ==> modify network ==> show advanced option ==> proxy) for its function. As such when the app is uninstalled, the proxy setting is still being remembered by the phone, and that causes the problem.
Simply delete the proxy settings on the selected network (aka don't use proxy), and it will work out.