Hi @hongngoctran77 ,
For customers experiencing any issues with their service, we recommend the best thing to do first is check if there's an outage.
Check our Service Status page for any known outages.
If you're on NBN, we have created this article that can guide you on How to Check for NBN Network Outage
If there are no known outages in your area, you can proceed with the troubleshooting steps indicated on these links:
If the issue persist, please send us your Customer ID or username via private message so we can check the status of your service.