Hi Ryan,
It seems that the hostname you used in that field might have mistakenly been entered incorrectly, as XmlEndpointUtility cannot parse it. Do you believe this to be the case?
If so, try opening LFDS.exe.config (in the same directory as the utility) with a text editor of your choice. I recommend you save a backup of this file before you begin editing. In this configuration file, you will find a line that reads:
<add key="TrustedPasswordResetHandlers" value="https://host.domain.com:port/lfdssts/ResetPassword" />
Where host, domain, and port correspond to your values. You can change the host, domain, and port (default 443) here to your intended ones, and save the file.
Once the host, domain, and port values are correctly set and the file has been saved, XmlEndpointUtility should work properly again.