Master HA instance with multiple slaves

Did you create the token on the remote instance or master instance?
You need to create it on the remote instance and add something like this in the configuration.yaml of the master instance:

remote_homeassistant:
  instances:
  - host: ip of remote instance
    port: HA port of remote instance
    secure: true
    verify_ssl: false
    access_token: token create on remote instance
    entity_prefix: "instance02_"