This error message comes directly from PayPal. Generally this means that you are trying to get permissions on an unconfirmed email address in your [PayPal] account. You will need to check your PayPal account and see if you have an unconfirmed email address in it.
If so, confirm that email address. You can check and/or confirm your email addresses at this direct link: Click Here to Check or Confirm Your PayPal Email Address.
Once you have it taken care of on PayPal's side, you will be able to authorize the WarriorPlus permissions with no problems.