Is your phone jailbroken? What you're seeing is most likely the result of OTA update being blocked by the jailbreak.
Yes it is
Sent from my iPhone 5 using Tapatalk 2
Jailbroken iPhones can not update via OTA.
Experiencing the same thing. On 5.1, I was able to check the version on this screen.
I know, i just wanted to check to see if their is an update available.
Sent from my iPhone 5 using Tapatalk 2
If you knew, then why are you asking? The OTA page has been disabled to even bring up the option of an update. You'll know immediately when an update is available when it's posted. It's already been confirmed however that 6.1.3 breaks your jailbreak anyways, so you'll want to stay away from updating. I'm getting the vibe that you'd "accidentally" update to the latest FW and lose your jailbreak.
with the update to evasi0n 1.2, the OTA update will not show up. You would have to check if there's a later version via connecting it to iTunes