There is a SharePoint site on the "Active sites" page of Microsoft admin console but the site is not listed in the Site collections section of Acronis Cyber Protection Console.
This behavior is by design.
The Active sites page in SharePoint contains all the new team sites and communication sites that don’t appear in the classic SharePoint admin center (to see the site list as it in the way it appeared in the classic SharePoint admin center, from the View menu, select Classic sites).
Acronis Cyber Protection Console groups SharePoint sites and places them to different folders: Groups, Site collections, Teams.
Group sites are listed in Groups.
Classic sites are listed in Site collections.
Team sites are listed in Teams.
In order to find your site, check all 3 folders: Teams, Site collections, Groups.