Fortigate SSL VPN with Azure AD DNS Issues

Question

I am having a strange issue with configuring FortiGate SSL VPN with Azure AD. I have configured SAML authentication successfully in the past using Google Workspace, but now I need to set up SAML in Azure AD. I am using this guide for reference: https://learn.microsoft.com/en-us/azure/active-directory/saas-apps/fortigate-ssl-vpn-tutorial

My current configuration will only work while using the IP address of the VPN in my entity-id and single-sign-on-url values. If I use the DNS hostname, I will get an HTTP invalid error when trying to connect to https://domain.com/remote/saml/login. The web login will also not redirect me to the Microsoft sign-in page. Changing the DNS name to the IP address resolved the problem. Please help.

I am running version 7.0.8. I downgraded from 7.2.2 for testing but that did not make a difference