Coincidence my NextJS project also facing the exact situation. When I click to start the service it says "failed to activate...." and the status is "Stop".
However when I visit my domain I can see the website is running. Also I am using the command "sudo netstat -tulpn | grep LISTEN" to find the process ID and able to see it is running on the port but the name is something like "next-router/" instead of usual "node".
I suspect somewhere in aaPanel that doesn't able to recognize NextJS framework's process name so it does not able to show the status as "Running"