Help Can't toggle 4g on

[tripton80]

I've recently lost the ability to use 4g, which I had until a few days ago, despite being in an area with pretty great 4g coverage. Trying to toggle the 4g antenna in the notification area does nothing, the toggle does not respond at all. I tried switching 4g on under Wireless and Networks but all I get is a status update saying "Turning On" before going right back to 4g being unchecked. The tech at the Sprint store hard reset my phone but nothing changed. Does anyone have a similar experience or am I just unlucky? I'm well outside of my 30 days and I'd rather not have to replace the phone if I can avoid it.