I had this problem. My app depended on cookies for authentication, and using Next.js apparently my cookies were not set on first page initialization.

I had this code, which was in charge of hitting a GET endpoint using Axios:

Bookings.getInitialProps = async ctx => {
  const response = await axios.get('http://localhost:3000/api/bookings/list')

  return {
    bookings: response.data
  }
}

I had Passport.js on the server side endpoint, but it failed to authenticate the user on the SSR page, because it didn’t find any cookie.

I had to change my code to this, adding the cookies to the headers:

Bookings.getInitialProps = async ctx => {
  const response = await axios({
    method: 'get',
    url: 'http://localhost:3000/api/bookings/list',
    headers: ctx.req ? { cookie: ctx.req.headers.cookie } : undefined
  })

  return {
    bookings: response.data
  }
}

The key to making cookies available in the backend was adding:

headers: ctx.req ? { cookie: ctx.req.headers.cookie } : undefined

to the Axios configuration.