I am using the service Auth0 as my Identity Provider and Service Provider for my wordpress website, which allows me to use them to store all my users login credentials. This also allows me to configure Auth0 as my service provider for any web apps so my users can log into my other web services using their wordpress credentials. I'd like the same thing for Zoho Desk. 

So far, I have configured Desk SAML with the settings for the SAML Auth0 application I created specifically for Desk, but after logging in, Zoho returns this message:

The Email address "null" specified is not valid. Please specify a valid email address.

Do you have any specific instructions on configuring Auth0? I've tried figuring it out for myself based on your current KB article but it only has instructions for OneLogin, Vault and Okta.