The issue with the IntelliJ plugin staying in the 'Initializing' state and showing the 'Failed to handle request' error message could be due to multiple factors. It is possible that there is a problem with the nodejs version in the environment. Additionally, there might be an issue with the tabby-agent.js file not being updated in the plugin's dist version. In some cases, updating the code repository or making changes to the environment can resolve the issue. However, it is important to note that there could be other factors contributing to the problem as well.