Why aren't my webhooks firing in the app and shop?

[Gretrix]

The app/uninstalled and shop/redact webhooks do not seem to be firing. I verify that the app/uninstalled webhook is in the site when I GET webhooks.json (and the topic, and all this is setup correctly), and also the https://appdomain.com/webhooks/shopRedact url is in the Shop Data Erasure GDPR webhook.

After 48 hours the shop/redact webhook never fires and the app/uninstalled webhook doesn't fire after an uninstall. Neither of these show up in the Webhooks section of the app in Partner Dashboard either. If they were firing, it should say 'Failed' or 'Success'.