Multiple accounts banned using a VPN, why?

I had 10 people create accounts for me on a astronomy forum. They go through some pretty serious rigor to make sure people don't create multiple accounts. Anyways, I used a VPN HPA which changed my IP every time I logged in. For a while, I was building up the accounts. I would post in different threads. One day I decided to post them all in the same thread... anyways, all of a sudden they all got banned.

Anyone know why this is? Can forums track machine numbers? Did I just need to clear my cookies?

PM sent - I may be able to help.

Portalweb I had a similar question. Can you PM me as well? thanks

I have 2 suggestions:
1) Always use the same IP for one account. It's suspicious if your IP always changes.
2) Use the incognito/private mode of the browser.

use CCcleaner between logins to remove everything and use the same IP per profile. you probably connected dots for them somewhere along the line. Easy to do