When it says “seen” under a member that has not yet responded to the event invitation, it means that the member has seen the invitation but not yet responded. This is whether they reply in the app or by e-mail.
We are unfortunately not able to do this with sms, but it is most likely that the person that you have invited will receive the invitation if you send out invitations with sms.
You can find the “seen” feature in events, and on the posts that you publish in a group.
