Can't connect to app after migrating from Heroku

Hello!
I migrated an app from Heroku, and while everything seemed to have gone fine, I can’t connect to the app. When I try the app url, I get DNS_PROBE_FINISHED_NXDOMAIN, and when I try using the IP I get ERR_CONNECTION_CLOSED.

The monitoring tab doesn’t show any activity following the migration.

For context, it’s a rails app, and I’m using Unicorn:

web: bundle exec unicorn -p $PORT -c ./config/unicorn.rb

Any ideas?
Thanks

Anyone? Help…

It looks like that app code is redirecting to www.<appname>.fly.dev, which isn’t a valid URL.