Currently Learning Toolbox does not support live collaborative editing of a stack by multiple authors. Instead each stack has one person who takes on the editing author role.
If you have been sent an invite link to create a stack, then the first person who follows that link will be given the editing role.
The person who takes on the editing author role will be able to add their co-authors’ names to the stack by adding their names in the Authors tile. However, their co-authors will not be able to edit the stack.
The editing author can also share the link to the stack with their co-authors (How do I share an stack from my computer) so that their co-authors can view the developing stack and email them with any feedback or suggestions. If they do this then they should make sure they change the stack permissions from Private to Public and Hidden (How do I set access permissions) before sending the link to their co-authors.
If your co-author has followed the invite link after you then they will get a message explaining that the link has already been used. If you would like to switch the editing role to them then just contact support and we will be able to do this for you.