Custom Object 02 and Account in one-to-many relation

Hi

I've set up a custom object (02) in a one-to-many relation with Account object.

I want to report on a field from CO2, account name and opportunity name.

I  see 4 subject areas in Reporting -

CO2 and Accounts,

CO2 and Contacts,

CO2 and Opportunities ,

CO2 and Service Requests  &

CO2s

 when I use the CO2 and Opportunities I get no results with these fields on the report - CO2.Accreditation, Account.Name, Opportunity.Opportunity Name

Any ideas? I am assuming, both CO2 and Opportunities being in 1:M relationship with Account, they don't need to be explicitely linked?

Thanks