my problem with registering expired tumblrs

alright a few days ago I was very motivated to find expired tumblrs with scrapebox.
After I bought SB watched some tutorials I found a good portion of expired tumblrs (300 in 1 week)

But the problem is whenever I found one with good metrics I can't register them. I usually get this and similar messages when try to register: "Try something else, that one is spoken for."

And yes I only saved expired tumblrs which are available ( according to SB )

Do I something wrong ? what's the issue, why is SB giving me results that I can't register

How do you have success with expired tumblrs with good metrics ?

thank you guys ..

I have a free tool that will do this check for you.

http://www.supagrowth.com/Expired-Tumblr-Hunter

It's a bit slow at the moment. I'm releasing a faster one soon with proxy support and other web 2.0s