I have solved the issue. The solution is to add the channel to the system setting by running the activity SetChannelPropertyMappings.
Now, another question is how to deploy that system-setting into a higher environment.
Do I need to move the instance with inskey of PEGAMKT-SYSTEM-SETTING DEFAULT? But Actually, this instance already moved to a higher environment before I implement push notification.
or Do I need to do manual setting on a higher environment by running the activity SetChannelPropertyMappings?
We would not recommend directly running the activity in the higher environment/production. Given you have already made the change in the lower environment and tested, it would be better to move the data instance you mentioned to the higher environment. One note of caution would be to confirm there is no other configuration change difference in that particular settings data instance between higher and lower environment. For example there are other setting like batch sizes etc which could have been directly modified in higher environment. Please compare the data instances XML to make sure there is no obvious differences between those.