The Raiden Wizard will display an Internal Server Error if an invalid project ID is provided. To solve this you have to manually delete the configuration file that got created.
The Wizard does not provide a way of shutting down the Raiden node. You have to cancel the process to stop Raiden.
Use the activity monitor for cancelling Raiden.
Use any Linux process manager for stopping Raiden.
You might want to delete configuration files if the wizard is taking a long time to start or if an invalid project ID has been provided and the wizard won't start at all.
Navigate to the following folder:
/Users/<username>/.local/share/raiden/
Delete desired .toml file/files.
Navigate to the following folder:
/home/<username>/.local/share/raiden/
Delete desired .toml file/files.