We have an ASP.NET web-based Enterprise Application deployed in Microsoft Azure. Currently the application uses SQL stored user accounts and Simple Membership to handle the user authentication.

We are trying to migrate the application to use SSO with Okta as an IdP, and have followed the documentation here: https://help.okta.com/en-us/content/topics/provisioning/azure/azure-create-enterprise-app.htm and what we are experiencing is:

1. When the user navigates to the web app, the authentication process initiates, which forwards the browser to the Okta login, and logs the user in.
2. Once logged into Okta, the app is displayed in the Applications section, and when the app icon is clicked or the application is launched, the user is forwarded back to a Microsoft error page stating "Invalid Empty Request".

I've spent the past 3 days working with Microsoft's support technicians who have been trying to figure out why that's happening, and their end result was that they believe the error is coming from the Okta side, because everything they see on their end says authentication is successful. I've been able to verify this by using the built in SSO testing tool in the Enterprise Application.

Thank you in advance for any and all suggestions.