Adding members to an existing group

I am the group administrator. In the past there was a button that said "invite members" and I could add new members by sending them an invitation. Now I don't see that button, so how can I invite new members into an existing group?

>1 kidlitfanatic: You can just send them a link to the group, either by a message on their profile or outside of the system (e.g. Email) and they can click the "Request to Join" button.