I have access to both Wi-Fi and 4G LTE. All the Google Play Store does is show that an app is trying to download, then it just stops and alerts me that the app can't be downloaded.
How much available space is there on the phone? Is the app compatible with your device?
I cannot download apps since the Marshmallow update, unless I turn off wifi. The VW rep told me Samsung needs to push some kind of update maybe?