Why does my iPhone's IMEI show as invalid?

[SHNXX]

I have a sealed iPhone I purchased from the apple store which I bought for work which I'm getting rid of because I never used it.
While I was trying to sell it, a lot of people asked me for the unlock status and the IMEI number.
So I tried entering the IMEI number to see if I could provide the information they were looking for and when I used multiple sites, it showed that the IMEI number is invalid.

What gives?
Why is the factory unlocked iPhone I bought from the LA's Apple store showing up as invalid?

 

[nox5]

You or new owner has to activate the iPhone with a SIM card

 

[Apples n' Stone]

In other words, seen as it has never been activated there will be no information to find.