Resister Error

I set up the Ultimate Auction for WordPress but when users try to register they are getting the following error:
There is suspicious activity on your network and registration can only continue with the webmaster’s assistance — contact him or her immediately.

I have set up in settings>general>membership>anyone can register but not having luck.

Fundraising page is here:

http://www.sprboston.com/seanssoapbox/?page_id=898

I’ve even tried installing the side bar registration widget.

Any advice?

https://ww.wp.xz.cn/plugins/ultimate-auction/