I am not seeing any replays for my backend, but they are working fine on my frontend.

Please keep in mind that there is technically no session replay for the backend.

What you can attach to the frontend replay are the errors from the backend. So, a better test will be to go on the frontend which should trigger a replay, and then you click a button to throw an error on the backend. Assuming everything works, you will see the error in the replay details.

You can find more information on Replays for backend errors in our docs and in this article.