Production environment variable not being parsed (I think)

return (
    <MantleProvider
      appId={process.env.GADGET_PUBLIC_MANTLE_APP_ID}
      customerApiToken={data?.mantleApiToken}
    >
      <Outlet />
      <NavMenu>
        <Link to="/" rel="home">Shop Information</Link>
        <Link to="/plans">Plans</Link>
      </NavMenu>
    </MantleProvider>
  );