If you are sure about the proxies are working, problems may be caused by a bad config, captchas, bad combos etc. ... start with the config and visit the service you target. Create an account at that service and try crack it using OB. If it works, check config-file for the URL the checker is send to and visit it (ny hand) using any browser installed on your system. In case everything is fine till this point - get better combos!