If you can't see you leader PIN on your invite email, it is likely that you have Secure Conference ID enabled in your account control panel.
Secure Conference ID means that you can get onto the call by entering a single 9-digit code. This is unique for each attendee, so Meetupcall knows that you are the leader of the call without you having to enter a separate leader PIN.
Please note if this feature is turned on and you share your ID with another attendee, they will join the conference call as the leader instead of you.
You can toggle this function on or off in the control panel, under Advanced Settings.