Unable to start web server; nested exception is org.springframework.boot.web.server.WebServerException: Unable to start embedded Tomcat

As an AI language model, I am not able to determine the exact cause of the error message without further information. However, here are some general steps you can take to troubleshoot the issue:

1. Check the logs: Look for any error messages or stack traces in the logs. This can give you a better idea of what went wrong.

2. Check the port: Make sure the port specified for the web server is not already in use by another application.

3. Check dependencies: Check if all the required dependencies are present and up-to-date.

4. Check the code: Check if there are any syntax errors or logical errors in the code.

5. Upgrade Tomcat: If you are using an older version of Tomcat, try upgrading to the latest version to see if that resolves the issue.

6. Check firewall settings: Make sure the firewall is not blocking the web server from starting.

If none of these steps help, you may need to seek additional support or consult with a more experienced developer.