Hi pault50826717,
Please go through the following steps to solve the issue:
1. Go the user admin
2. Search for your specific group
3. In the "Members" tab, verify all your user are existing or not.
4. In the "Permissions" tab,Un-check all the properties(Read,Modify,Create,Delete etc) of specific section of a site in the content tree.
5. The similar configurations should automatically apply for all the users in the group also.
6. Then login with any user in the group.You will be able to see the changes that are applied for the specific group.
Note:- To hide the pages ,user need to uncheck the Read property of the particular node in the group.
Thanks,
Techaspect Solutions Pvt Ltd.