I would like you to provide more details on the issue.
By reboot, do you mean reboot of router or some connected device?
What light and how are you turning off?
What do you mean by "LAN does not turn on"? Is the interface shown as offline in in the WebUI, or are you not able to access the router via one of the LAN ports? Are the lights of the port not operational?
Is this an issue with a single port or all of the LAN ports?
Could you share the troubleshoot file, if possible? Please, make sure to replicate the issue, then access router's WebUI, go to System -> Administration -> Troubleshoot section and download troubleshoot file from there. Attach the file by editing your question.