No idea, you haven't been very specific with what your current usage is. The page where the Authorize.net payment is being made must be HTTPS. You need a valid SSL certificate and working HTTPS to use Authorize.net. CBSubs will attempt to redirect to HTTPS when attempting to make an on-site purchase. You can disable this in CBSubs > Settings > Credit-cards, but I don't recommend it and CBSubs will throw a huge warning banner at the top if not in HTTPS.