I have been emailing to ibookstore@apple.com and ibookstore_applicationsupport@apple.com for a few months to solve the sign-up problem.
In late January and early February it took ibookstore@apple.com 2 weeks to get back to me ... with a useless reply. And it took ibookstore_applicationsupport@apple.com 4-5 days to reply, with one sentence only: "we've resent the confirmation email" ... which was still useless to me. -- but anyway they replied.
Since late February they never ever replied again ... I sent them 1 email per week, and the earliest email has been like three weeks. No replies at all, not even one sentence.
I thought there might be something wrong with our company email server, so I tried to send them emails again today with a new gmail account. Guess what:
I cc the emails to a few of my other email addresses, and none of them received the emails I sent to ibookstore@apple.com and ibookstore_applicationsupport@apple.com! Those emails just disappeared! I have no idea what's going on now ... have they moved out to another planet???!!!