The backend variable for the preview branch staging for my project is not being picked up, but the front end variables are. This is causing all modals to fail in the staging environment. We'd like to ideally avoid deploying features to production and have the staging environment to ensure products are working successfully. All the environment variables on the backend are coming back as undefined. They work in production and in local development so not sure why it's not being picked up in preview branches/designated stage deployment.

All help is appreciated, thank you.