ORA-16816: incorrect database role

In Data Guard, for some reason, standby database rule are incorrectly shown as primary database, while primary database shows as standby rule.

DGMGRL> show configuration;

Configuration - TESTDB
  Protection Mode: MaxPerformance
  Databases:
    TESTDBSTY - Primary database
      Error: ORA-16810: multiple errors or warnings detected 
             for the database

     TESTDB - Physical standby database
      Error: ORA-16810: multiple errors or warnings detected 
             for the database

Fast-Start Failover: DISABLED

Configuration Status:
ERROR 


DGMGRL> show database "TESTDBSTY";

Database - TESTDBSTY

Role: PRIMARY
Intended State: TRANSPORT-ON
Instance(s): TESTDBSTY
Error: ORA-16782: instance not open for read and write access
Database Error(s):
ORA-16816: incorrect database role

Database Status:
ERROR

How to fix it ?