I ran a PS script from this site - https://techcommunity.microsoft.com/t5/SharePoint/O365-Global-Admin-has-no-access-to-recent-SharePoint-Online-site/td-p/30031
It made a AD Security group an owner of all the group team sites that get created when you create an O365 group. I am able to see the group as a site owner, as well as when I go to check permissions, I see the group and a specific user in the group as having all access, however attempting to navigate to the page shows the "Sorry, you don't have access to this page" screen.
Before my configuration above, I saw in the admin page, Company Administrator is the admin for the all site collections, and upon research, the O365 global admins should fall into that group, but it gave the access denied page for group sites the admin's were not explicitly shown as a site owner.
I also tried adding a regular O365 cloud group that is not in the AD, however that didn't give access either.
Any thoughts on why the sites are indeed showing the AD group is an owner and shows the proper permissions, but access is still denied?