User account blocked from logging in

Hi

For cbpn.io, I can log in fine with the site admin account, but when I try and use a test account set up for myself, 'neilmcevoy', I can no longer log in.

In most cases it just gives me an endless spinning wheel, on this last occasion it gave me this errror message:

"503: Service Temporarily Unavailable
Too many IP addresses accessing one secure area!
Please contact Support if you need assistance. "

So something has decided to take issue with the fact I'm logging in from two different accounts from one location.. I'm wondering if it is this service which I recently installed: https://cleantalk.org

It's a very efficient spam blocker, or is this a core Wordpress feature?

thanks, Neil.