Proxy account registration problem

Hi guys! I just can't register new account with proxy, i bought 10 proxies from instantproxies com
but its not working, when i try to register new account(from web interface) it says "error, try again later" and its on every proxy i have.

What i am doing wrong?

What browser are you using? You need to use incognito if using google chrome.

Also, it's possible that those proxies have already been abused for creating accounts. Semi-dedicated, dedicated? What kind of proxies did you buy?