This. It has become difficult to bypass the biggest social networking sites. But VPN can really help you get through this.The detection systems have advanced so much most of big sites configured their site to identify the proxy, tor etc. VPN is only good way.
its before creating account.isn't because of the proxies. They don't care if you use proxies, VPN or if you log in from a public wi-fi. Many people are using VPN/proxies to access twitter and they are legit users
You have issues because you abused in some way twitter (too many follow/PM ?) or you have logged in from a proxy which is in a different zone than your last logins