How to fix the issue when Oracle TNS service cannot start?

The Oracle TNS service may not start due to the following reasons:

1. Make sure that the Oracle database instance is running, as the TNS service depends on the database instance’s operational state.
2. Check if the TNS Listener configuration file is correct, usually the listener.ora file.
3. Ensure that the port being listened to by the TNS Listener is not already in use by another process.
4. Check the log files of the TNS Listener to see if there are any error messages.
5. You can try restarting the TNS Listener service by using the lsnrctl command.
6. Check the firewall settings to make sure that the ports are open.
7. Check if the network connection is working properly by testing the status of the TNS connection using the tnsping command.

If none of the above methods solve the issue, it is recommended to contact Oracle technical support for further troubleshooting and resolution.