Guests can't RSVP from Facebook
Please go to Manage Invitation and Edit Details, and Guest Options. Under Guest Options, please check the box to Allow Guests to Share Event. There is also a little question mark Help Button which states that in order to share this invitation on Social Media networks, this box must be checked.
If guests are still unable to RSVP, this can also be due to the host already inviting them on the guest list. For instance, if "Tom, email@example.com" is already invited on the guest list, and the host sends him the shareable link, if he tries to RSVP through the link, our site will tell them that he is "already on the guest list". This prevents the guest from adding themselves on the guest list and thus having TWO duplicates of themselves on the guest list.
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