It appears that the dbplan did not get run. It is possible that it is either not picking up everything quite correctly, or you just need to run q2 run_db_plan.
That example extension unfortunately will not run out of the box. The stored procedure in question is basically used to get configurations for different product types. So you can implement a config via the self.wedge_address_configs property.
Feel free to submit a Support ticket on the developer portal and we can help you get up and running.