Sometimes your minerstat application cannot properly communicate with minerstat dashboard as some other application reserved the port 3333 that is needed for communication between your rig, mining client, minerstat software, and minerstat dashboard. If this is the case, you will need to close the application down. To find such applications, you can use the following commands.
When port is already in use, mining client usually starts and shows errors, but minerstat application cannot read mining data from it.