Hi @Danny_Kurnianto,
It is very difficult to help you without knowing specifically what error it is, and even if you get a message about SMTP connect() failed, it could be several factors.
I suggest you read the official documentation https://docs.pkp.sfu.ca/admin-guide/3.3/en/email to make sure you have a correct configuration.
Are you using a specific SMTP server?
What can you find in the error_log file of your OJS installation?
In order to help you we need more information.
I hope you find this information useful.