Networking is fine on both data and WiFi. Credentials? I assume you mean my Google account? I've tried using an existing gmail account but that didn't work and I tried creating a new gmail account, that doesn't work either. It signs in OK but all I get is "no connection". The web version works fine but I need to register the handset through the app before I can download anything.
It's a pretty common problem from what I can gather, I've tried all the online suggestions but they don't work, even factory reset. I can't uninstall the app, it's a protected one, so I can't even try the usual uninstall, re-install trick.