ENV variables which work locally with a .env file, do not work on app platform at runtime

The Problem

Our node.js Nuxt.js app uses env variables connected with dotenv. When running in dev mode and in production build locally with a standard .env file, our env’s work fine.

In Digital Oceans App Platform, we have added the env variables to the app level env settings and deployed the app: API_BASE_URL = https://api.example.com

But the env’s dont seem to be working.

How we’ve tested this

In one of our main JS file we have console logged an env as follows: console.log(process.env.API_BASE_URL);

This log returns the correct env locally both in build and dev mode. But in App Platform, it returns undefined. So this suggests, the unique way in which App Platform handles env variables is not working with our set up (which I would have thought was pretty standard practice with a normal .env file in the root and using dotenv

Primary Question

Does anyone know what else is needed to get Digital Oceans App Platform env variables to work correctly at runtime?