You should look at the full fop2 debug with 511 and see what happens after each queueadd request, what is the actual command being set to the asterisk manager and the asterisk response.
As for adding yourself to queues after login in, you do not need the plugin, just click on the presence icon (green/orange led) on your extension, where you will have the option to add yourself (or remove) from any visible queues.
Best regards,
