To configure access to the Seamless Overview, login as Seamless Administrator and add the users or security groups to the specific SharePoint Group “<Site Name> Visitors”.
Therefore, open the site with SharePoint groups in your Seamless Overview Page
Select the <Site Name> Visitors Groups
To add users or AD Security Groups, click on “New” and “Add Users”.
It’s good practice to add “Everyone except external users” to the group of visitors. This allows access for all users in your tenant to the Seamless Overview from where they can open Seamless Workspaces.