Did you install it under an admin account so the plug in is available to all users?
Yes
Do not use Java 9. It has been out only for a few days and most software doesn't support it yet, including Traccar.
But before I install Java 9, I have Java 8 for months and then the error occurred so I try to download the newest version for hoping it will fix the issue. What I need to do ?
I would recommend to get Java 8.
It says it requires Java Runtime Environment version 7 or later. But i have the most updated java version (9). What can i do to fix it ?