"Unable to open": what it means
Your access level does not include that area; ask an Admin.
When BMS says Unable to Open followed by an area, such as Unable to Open Settings, your access level does not include that area.
Ask an Admin at your firm to change your access or permissions; see Edit a colleague’s permissions.
Unable to Open This Page with “It does not exist, or it has been deleted” means something else: the record has gone, or the link is wrong. Find it again from its list.