Polycom 501, unable to do to a blind transfer

I’m attempting to do a transfer via ## then the extension. But as soon as I dial the second # I get a fast busy. I’m guessing its either a dialplan issue or some config change I need to make in the sip.cfg.

If anyone has any ideas I would appreciate it.

Do you have the access code enabled on the feature codes page? and if so, is it correctly configured to use ##?