By default, new members of a group can only see messages sent after they join. When this feature is enabled, new members can also retrieve messages sent before they joined the group.
Note: To use this feature, you must first enable Cloud Storage for One-to-One and Group Messages.
To enable this feature, go to the Basic Features page in the Console and turn on New user group history access.
If you have any questions about this feature, feel free to submit a ticket to us.