Spaces app forever in "Running..." state while trying to launch

I tried to build a demo app on huggingface spaces, just a vanilla Resnet classification model app.py · vardaan123/COSMO-demo at main. The log shows it starts running but there is no UI in the ‘App’ tab. It shows “Running…” on the top right but the app screen is blank and doesn’t launch even after 10 minutes.
When I click on ‘App’ again, it restarts and then complains that the port is busy. Is there something obvious I am missing?
Debugging:

  1. It works when I try to run locally
  2. I restarted the space but still no success.