when a new instance is being added to a RAC DG setup after the broker configuration was created then we might see this error message

[oracle@ole71002 trace]$ dgmgrl sys/'oracle'@ICP01RKA
DGMGRL for Linux: Release 12.2.0.1.0 - Production on Thu Nov 25 09:56:45 2021

Copyright (c) 1982, 2017, Oracle and/or its affiliates.  All rights reserved.

Welcome to DGMGRL, type "help" for information.
Connected to "ICP01RKA"
Connected as SYSDBA.
DGMGRL> show configuration

Configuration - ICP01RKA_DR

  Protection Mode: MaxPerformance
  Members:
  ICP01RKA - Primary database
    ICC01RKA - Physical standby database
    ICC11RKA - Physical standby database
      Warning: ORA-16632: instance being added to member profile

Fast-Start Failover: DISABLED

Configuration Status:
WARNING   (status updated 44 seconds ago)

if you check the standby database it shows only 2 instance

DGMGRL>  show database 'ICC11RKA'

Database - ICC11RKA

  Role:               PHYSICAL STANDBY
  Intended State:     APPLY-ON
  Transport Lag:      0 seconds (computed 0 seconds ago)
  Apply Lag:          0 seconds (computed 0 seconds ago)
  Average Apply Rate: 11.92 MByte/s
  Real Time Query:    OFF
  Instance(s):
    ICC11RKA_1 (apply instance)
    ICC11RKA_2

Database Status:
SUCCESS

but if you check there are now 3 instances

[oracle@oel71603 ~]$ srvctl status database -d ICC11RKA
Instance ICC11RKA_1 is running on node oel71601
Instance ICC11RKA_2 is running on node oel71603
Instance ICC11RKA_3 is running on node oel71604

to resolve this error you need to remove and add your standby databases again in broker configuration

DGMGRL> remove database 'ICC11RKA'
Removed database "ICC11RKA" from the configuration
DGMGRL> show configuration

Configuration - ICP01RKA_DR

  Protection Mode: MaxPerformance
  Members:
  ICP01RKA - Primary database
    ICC01RKA - Physical standby database

Fast-Start Failover: DISABLED

Configuration Status:
SUCCESS   (status updated 59 seconds ago)

add database back

DGMGRL> ADD DATABASE 'ICC11RKA' AS CONNECT IDENTIFIER IS 'ICC11RKA' MAINTAINED AS PHYSICAL;
Database "ICC11RKA" added
DGMGRL>  show configuration

Configuration - ICP01RKA_DR

  Protection Mode: MaxPerformance
  Members:
  ICP01RKA - Primary database
    ICC01RKA - Physical standby database
    ICC11RKA - Physical standby database (disabled)

Fast-Start Failover: DISABLED

Configuration Status:
SUCCESS   (status updated 37 seconds ago)

enable the newly added standby

DGMGRL> show database 'ICC11RKA'

Database - ICC11RKA

  Role:               PHYSICAL STANDBY
  Intended State:     OFFLINE
  Transport Lag:      (unknown)
  Apply Lag:          (unknown)
  Average Apply Rate: (unknown)
  Real Time Query:    OFF
  Instance(s):
    ICC11RKA_1
    ICC11RKA_2
    ICC11RKA_3

Database Status:
DISABLED

DGMGRL> ENABLE DATABASE 'ICC11RKA'
Enabled.
DGMGRL> show database 'ICC11RKA'

Database - ICC11RKA

  Role:               PHYSICAL STANDBY
  Intended State:     APPLY-ON
  Transport Lag:      0 seconds (computed 0 seconds ago)
  Apply Lag:          13 seconds (computed 0 seconds ago)
  Average Apply Rate: 11.72 MByte/s
  Real Time Query:    OFF
  Instance(s):
    ICC11RKA_1 (apply instance)
    ICC11RKA_2
    ICC11RKA_3

Database Status:
SUCCESS

now check the configuration

DGMGRL>  show configuration

Configuration - ICP01RKA_DR

  Protection Mode: MaxPerformance
  Members:
  ICP01RKA - Primary database
    ICC01RKA - Physical standby database
    ICC11RKA - Physical standby database

Fast-Start Failover: DISABLED

Configuration Status:
SUCCESS   (status updated 9 seconds ago)