Trusted Advisor can be accessed in individual AWS accounts or, via the Management account, for the entire AWS Organization.
By default, Trusted Advisor is configured not to evaluate all accounts in the Organization from the Management account, rather for each account to only evaluate itself. Enabling the Organizational View for Trusted Advisor allows the AWS Organization's Management account to evaluate all accounts within the Organization.
Depending on your account ownership model, you must take different actions to enable this feature.
Customer-Owned Management Account
If your organization owns its own Management account, follow AWS's guidance to enable this feature.
Reseller-Owned Management Account
If your organization's Management account is owned by a reseller, you must raise a support case requesting that the Organizational View be enabled for your AWS Organization.