Hello Troy,
several people reported already the same error the last couple of weeks. For some it worked to delete the instance and create it new. When the shared instance is created all required rights should be assigned.
Independent of that you can also create a MDC (SAP HANA Multitenant Database Containers (MDC) scenarios now on trial landscape) on the HCP trial account. So you would not have the restrictions of the shared trial instance.
Regards,
Florian