Normally, if a site wants to show notifications, Firefox will prompt you for approval. If you granted approval and want to revoke it, here are two options: (1) While on that page, tap the lock icon in the address bar. A pop-up panel should list customized site permissions and allow you to change them. (2) menu > Settings > Site Settings Scroll all the way to the bottom and tap Exceptions. This should load a screen showing all sites that have customized permissions and let you clear individual site customizations or all customizations. Did either of those methods work?