Our company XYZ has other acquired other companies. These companies are not completely on the same network as XYZ
When we try to activate their install, we get a license check error. However, they are able to access our foundation form the web at http://winshuttle.XYZ.com.
Can you offer some network connection suggestions? Proxy? Thanks.
To overcome this issue first user need to verify that the Sharepoint team has made the synch of AD(Active Directory ) between domains for the cross functioning.
Also Network team need to check the Ports are open as well for those domains.
To check the sharepoint set up you can login to Foundation site as admin.
1) Settings - People and Groups- Try adding the user with different domain.(screenshot attached for reference).
2) Now on the Foundations site - Select Tab - Users - Add users- Try adding the users with different domains.
Also; please go through below article and test the same; this will confirm whether the IPs for the new domains are accessible or not.