By default, Bitrix24 users cannot access CRM elements that they are not responsible for. You need to configure access permissions so that users would be able to access such elements.
Go to CRM > Settings > Permissions > Access Permissions.
All new employees are automatically added to Bitrix: Employees group with a Manager role.
Users having this role can access only those CRM elements that they are responsible for (excepting "companies" - all users have access to all companies).
If you want to, you can select All option for all actions and for all CRM elements. In that case, all users with Manager role will be able to access any CRM elements.
"All open" option
One of the access levels is called All open.
If you select this option, users will be able to access CRM elements they are responsible for, CRM elements related to their department or subdepartment, and CRM elements that have been marked as Available to everyone.