Someone who registered using the Register Page for my event wants to bring a guest - why can’t I add a guest to their reservation?

You can only add another guest (or guests) to a confirmed guest who was invited (by sending them an Invite Email) - not to a guest who registered through the Register Page. The reason for this is because Seatrobot assumes that Email Invites are used for events where you want to control precisely who can attend, and how many guests they can each have.

Register Page guests register from a public page (using your Register Page link) - so for these events, Seatrobot assumes you just want people to register - and don’t mind if they share that link with others you don’t know.

If someone else needs to register as well, you can simply send them the link - and after they register, if you want to keep the two guests together you can Link them in Guest List.