The option being missing has been previously reported but was meant to have been fully fixed a while ago Checking in-game it shows up for me on all characters including the one that I haven't completed the Act 3 questline on. For BNGHelp to pass it on they'll want a clip or screenshots showing the option being missing and the current quest step. FWIW, you can try using the legacy fireteam finder (either on the app under fireteams->legacy or on Bungie.net [url=https://www.bungie.net/7/en/Fireteams/Search]here[/url]) to put together a team. If I'm remembering correctly there shouldn't be any expert steps within that questline but that requirement was instead included in the catalyst trait quests which are separate.