Hey Guys,
There’s a difference between what happens when a new user talks to a bot as opposed to a returning user:
A new user has to click the Get Started button. This automatically sends a message of /Start to the bot, which is what triggers the welcome message to run.
A returning user returns to an open window that maintains state from previous sessions and does not have any way to trigger a flow or even know a user hasn’t opened that chat window by mistake until the user sends it a message, interacts with a persistent menu etc.
Unfortunately a message does need to be sent to the bot in order to be able to trigger a flow or the welcome message. For a returning user this does have to be a manual process by the user.