I also made this account just to share how I solved this (on a Samsung Galaxy S5). I was constantly showing Download Manager attempting to download an update, but never making any progress. I connected to a Wi-Fi network and suddenly the updates all happened.
In Play Store->Settings I had Auto-update apps set to allow updating at any time. I have since tried setting that to WiFi only and then back to any time; it now downloads with no problems over the 4G network. I suspect that changing the Play Store->Settings to something else and then back again would have fixed the problem alone as well.
In Play Store->Settings I had Auto-update apps set to allow updating at any time. I have since tried setting that to WiFi only and then back to any time; it now downloads with no problems over the 4G network. I suspect that changing the Play Store->Settings to something else and then back again would have fixed the problem alone as well.