I can't get my credit report from Equifax, and I can't sign up to Credit Karma for the same reason: When verifying my identity by asking about loans/mortgages, both places ask me about a mortgage I got in 2011, which is unanswerable -- I have no mortgage and never have had one. So I clicked 'None of the above' on all the questions about the mortgage, which was correct, since as I said already, I don't have a mortgage.
Also, very recently I applied for a credit card and was told I had no credit history, so even if my identity was stolen, how did the thieves manage to get a loan in my name??
Update: I've now emailed Credit Karma about this, and am awaiting a reply.
Edit: Since applying for the credit card, I have gotten a loan (co-signed) and have made payments on it for 5 months now, never being late. So it seems I should have at least a little bit of credit history by now.