Call MY Sip IVR (Success)> Enter 88 (Success)> Enter in Conference # (Success)> Play Join Message (Success) > Then I get the message The That is not a valid conference number please try again and it hangs up.
It lies! If it were not a valid conference then I would not have received the Join message or even allowed to authenticate through.
Just a formality. The result is the same if I create an inbound route which routes direct to the conference or I have option 88 go directly to the conference room chosen through freepbx.
The custom extension asks for the conference room… so its like a lobby area.