Cannot add a database target to an existing group

13.5

can somebody help to add target to a group :

Has tried these options without success:

-from the console --> group --> select the group --> edit group

and cannot add

-from emcli command

emcli modify_group

emcli modify_group -name=Deve-xxxx-Grp -add_targets=xxx.world_1:oracle_database

Error: Administration Groups can not be modified

===>

-from the target database xxxx --> target setup --> add to group --->Thre group is not visible. Only this message:

Select the group(s) to which you need to add this target. Only groups on which you have at least Operator privileges are shown below.