I notice they've changed their join page options to include a 1day free trial as well their $1 3 days trial. I previously had the $1 3 day trial option selected on all my links but today when checking the join pages from these links they now point to the free trial join page (no $1 option).
I had a few sales in the last couple of weeks register for $0 and other sales have been just about non-existant. I've emailed them about this twice over the last couple of weeks and get no response.
So yeah, check your links, especially if you had the $1 trial option picked.