Session API questions

Greetings;

I inherited an application from a previous developer who turned over scant documentation. We have a running application with embedded PowerBI reports, and this runs fine.

We are trying to stand up another instance of this application, and cannot seem to get the embedded Power BI reports to function.

At this stage, we believe one issue is the Session API. When the user clicks the link to open the embedded report, we call .../api/2.0/Session, and we get similar to the following in response on the system that is functional:

date: "Tue 21 Feb 2023 17:45:13 GMT"

setCookie: sqlAuthCookie="...." (redacted)

server: "Microsoft-HTTPAPI/2.0"

On the non-functioning system, I get this:

connection: "close"

date: "Tue 21 Feb 2023 17:42:11 GMT"

server: "Microsoft-HTTPAPI/2.0"

Can anyone point me in the direction of how I can find out why my session is not being established properly, any logging I can enable, or other troubleshooting ideas? My report server is running and functional on both systems, but just not integrated within the calling application on the second.