After the npm install finishes, the app should restart. You can then close the Terminal and see the app in the preview and submit the url to pass the challenge as long as you have the correct environment variable and value in .env file.
Glitch will spin down your server every 30 minutes I think. This means if you haven’t opened it in an hour or so, your app may take a long time to spin up.
There should be a debugger in Glitch you can open to check to see what the issue is.