A Tarantella Administrator can specify that a Tarantella server is not available to users (--server-login disabled). This prevents users from logging in to that server and starting new emulator sessions.
If an Administrator accidentally denies access to all servers in the array, you can't use Tarantella to access Array Manager and re-enable logins.
If this happens, you can either:
tarantella arraymanager
command and then re-enable Tarantella logins for a server, or
tarantella config edit --server server --server-login enabled