Most likely you'll need to turn off LTE and use CDMA only.
Many are having issues with the S5 on Sprint and LTE/Spark. And that has been the official response from Sprint on the 'fix' for now. It's been ongoing since April, I can't turn on LTE otherwise I can't receive or make calls.
That seems odd. Are you able to use any other features that require a Data connection without being connected to WiFi? Please let me know.
Sprint Social Care
Balony. Its not "odd" KC. The reason they aren't getting emails is because when running on 3G, which is all this stupid phone EVER runs on, it won't do anything that requires data and the internet. This phone + Sprint = junk.