I’ve been experiencing this tunnel issue over the last 24 hours, and using my own ngrok tunnel works.
In a new terminal tab run
ngrok http 3000
and then in the other terminal tab, from within the repo of your app run shopify app dev --reset --tunnel-url {ngrok https url}:3000
For instance, mine was:
shopify app dev --reset --tunnel-url https://5127-46-149-103-112.ngrok-free.app:3000
hope that helps!