"invalid security key"

I’m not sure why, but comments aren’t working on my wordpress blog. I can comment when logged in as administrator, but when anyone else tries, it tells them they have an “invalid security key”. It doesn’t matter if they sign in with facebook or twitter, or if they manually fill in the name etc fields.

I have deactivated all plugins that have anything to do with comments with no effect, I’ve even tried other themes and tried deactivating akismet. I don’t know what else to do…please help.

https://www.ads-software.com/extend/plugins/comments/