If the video is Private, it will not play for other users. The video must be Public or Unlisted. For more information, please visit YouTube's help.
If you are using "adult" content, people with "Safety Mode" on will not be able to watch it. This is tricky to fix. Basically, the attendee needs to go into their personal YouTube settings and turn off "Safety Mode". Please visit YouTube for more help.
My video isn't private and i'm not using an adult content , but still people can't see my videos !