If you see something like that:
DGMGRL> connect /
Connected.
DGMGRL> DISABLE CONFIGURATION;
Disabled.
DGMGRL> edit database "dbXX" set property 'LocalListenerAddress'='(ADDRESS=(PROTOCOL=tcp)(HOST=XXX.XX.au)(PORT=1521))';
Error: ORA-16541: site is not enabled
Configuration details cannot be determined by DGMGRL
DGMGRL> ENABLE CONFIGURATION;
Error: ORA-16541: site is not enabled
Configuration details cannot be determined by DGMGRL
DGMGRL> exit
It may well happen after switchover operation.