Add New Members not working

I have successfully added a group but when I try to add a new member I get this message: The following users could not be added to the group: “name”

I have tried adding a first and last name, just a first name, and an email address. I have also tried changing the settings to Public and then private. I have checked the box for All Group Members to be able to invite others to the group.

What can I do?

Thanks! https://www.peddlersgear.com

https://www.ads-software.com/plugins/bp-group-documents/