At the moment, Fantoo collects notifications sent using the HTML5 standard, which has been fairly well adopted by web app makers, e.g. Slack and WhatsApp.
There are other ways to send notifications over the web though - in 2019 we'll be working on ways to pull those in. We know how important notifications are, and we want as many of them as possible in one place for you.
Before you write off your app's ability to send notifications, check that 'desktop notifications' or 'desktop alerts' are enabled in its settings.
Here's an example from WhatsApp (within its settings menu):