When you check for an update, you are pinging the carrier, who checks to see if you're scheduled to receive it. If you are, then you'll get notice that an update is available to download. This means that if you're scheduled to get the update on, say, January 25 at 3:47am, your phone will say that it's "up to date" despite the fact that others on this forum had been getting it since the 16th.
In your case, you were unable to ping the carrier, or the carrier was unable to reply (or check) at this time. You should be able to later on.