Sorry you're stuck but there's almost always a pretty easy fix! Do NOT try to start all over again, eg. uninstall Max's Pitch Package, etc. That can make things worse.
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I did few steps wrong, so I simply went back clicking the ”back” option. From step 80, I reached back to step 58. I entered “meeting” for label and object name auto filled with “meeting”, but it shows error in the object name and says that “the object name is already in use”. Can anyone please help with this?
Yeah, backing up in your browser doesn't undo anything. You've already got your Meeting object. You don't need/want to be creating another one. That would cause a bunch of trouble. If you made some mistakes in creating the Meeting object, you're better off just fixing them, rather than creating a whole new object.