Hello,
If you are added to the project as a Project Billing Manager, the project may not show up in your dashboard so this is likely just a permission issue. You would need to have the organization admin or maybe someone else who was an owner add you to the project as a viewer at least. There are other permissions that would allow you to see the project other than just being a viewer but project billing manager is not one of them. This documentation may be helpful in your case.
If you are already an organization admin, then it’s possible that the project was never added to the organization but it’s linked to your billing account. If you believe this is the case, please contact the Google Cloud Platform Billing support and explain the situation. You could also try opening a Google Issue Tracker and we could possibly verify on our end what’s the issue preventing you from seeing this project.