If you can use the same email just change your birthday to make yourself 18. If not make a new email and try signing up again using your "new birthday". I know people who are on there who are only 14 so maybe it is something else... make sure you check your email and do the whole 'click on the link below to confirm your email' Hope that helps! =)
just adjust the year of your birthdate. because it appears that you're 17 yrs old. they allow 18 yrs old up
you have to be at least 18...
After a day, Facebook gets unblocked so you can always try again and fake your age and decide not to show it to public.
Hope I helped.
Maybe the email has already been used