A 403 Forbidden means that the server isn't properly configured to allow you to connect from that IP address or you're actually banned from using it, which I highly doubt since you've been using it until now.
Try logging in with an Administrator username and check the permissions for the user you're commonly using, then repeat the process and login normally.
I couldn't find any documentation for the Microsoft LEAF Professional 2013 because I can't find it on the web or on the Microsoft website. It's either discontinued or used only by customers.