Green crack auto almost 42 days old and still not flowering?

I'd give it another week or two, she may just be a late bloomer. If it has unfortunately missed the rude gene, you can force her into flower with 48 hours of darkness (optional but it will speed up the process) and then a maximum of 14 hours of light per day from then on (I personally do 12/12 with photoperiods, but 14/10 is possible). Not ideal if she's in a tent with other autos that you want running at 18-20 hours light per day, but they'll deal with it and I've grown perfectly fine autos in the past under 12/12.