While trying to call the REST endpoint to add an existing member to a group
we are getting the error "You do not have the 'manage membership' permission for [group name] that is required to complete this action."
This call is being made as an administrator (has API Administration role, which has Manage Membership permission).
Is there some additional setup or another permission that is necessary to get this call to work?
Does the user have the manage membership permission granted in the group? It's a different permission than the site-level member management permission.
How do we grant that?
Navigate to the group, click the pencil icon, Manage Group > Permissions, choose a role, ensure that under "Group Permissions" that "Manage Membership" is enabled.