They want proof of 2007. According to the above you had a 2007 tax return that wasn't actually filed in 2007 and it's listing an address that you lived at later so they're saying that's not good proof of 2007 and since your transcript also says you were gone in 2007, that didn't work to fully prove 2007 (it shows an absence). So you just have to find other proof from 2007 and write a statement explaining what happened and proving what you say to the best of your ability.