Please follow the steps below
- Go to the general configuration page
Select an option where the add-in will get users list. There are 3 options type
If all users in site. Select All user in site
If all users in users info list. Select Users from List 'Manage Users information'
If all users in SharePoint Group. Select another
If you select the SharePoint Group, Please make sure that "Who can view the membership of the group?" in Group Settings is everyone