Next JS User session data successfully saves locally, but fails to save when deployed to AWS

Question

In an app I'm building, a user logins in (validates through Magic Auth), and we save the user data in the session variable (using Iron for session management):

export default withSessionRoute(async (req, res) => {
  try {
        const didToken = req.headers?.authorization?.substr(7);
        if (didToken) {
          magic.token.validate(didToken);
          const metadata: any = await magic.users.getMetadataByToken(didToken);
          const response = await createUser({ email: metadata.email });
          req.session.user = response.data.user;
          req.session.userMetadata = metadata;
          await req.session.save();
          return res.send({ user: response.data.user, authenticated: true });
       } else {
          res.status(200).json({ authenticated: false });
       }
      } catch (error: any) {
        console.log(error);
        res.status(500).json({ error: error.message });
      }
});

This works totally fine locally (req.session.user remains filled with user data), but for some reason on my deployed app, it does not work at all. It still returns the user data in "req.send", but the session variable is empty, so it does not seem to have saved.

Any ideas on what the issue could be?