You may receive an error "Not Authorized" when attempting to view either Setup -> Accounts -> AWS, or drill into an AWS account from the Account Name field within Asset reports.
This error is caused due to your Role/Role Document lacking the: AWS -> Account -> Read AWS Account permission.
Role Document -
Roles -
Request that your administrator activate this privilege against your assigned Role/Role Document, and then allow the change to propagate throughout the platform for 30mins before attempting to access the AWS account via either - Setup -> Accounts -> AWS, or drill into an AWS account from the Account Name field within Asset reports.