Tumblr account terminated?

That's strange. Sorry I'm only just seeing this now! Did bạn ever find out what caused this to happen?

One possibility, I suppose, is that bạn might have the same external IP address as a tumblr user who got banned for life. Even though external IP addresses are supposed to be unique, there's really only so many of them and sometimes freak things like that happen. However, they also change from time to time. bạn might find (if bạn haven't already) that if bạn try to create an account again, bạn will have no problems.

(BTW I've apparently shared external IP addresses with people from Nhật Bản and New Zealand before. I live in England.)

It could have been something else of course, but like I said, it's worth trying again if bạn haven't yet. Whatever it was, it could have easily just been an in-the-moment freak thing that will never happen again.