Microsoft has announced that they will no longer support the Cortana digital personal assistant app on Android and iOS devices starting in 2020. In support articles for the UK, Australian, and Canadian markets, Microsoft has stated that they will no longer support the Cortana digital assistant apps on iOS and Android stating on January 31st, 2020. Instead, Microsoft will be integrating Cortana into the Microsoft 365 productivity apps. At that time, any Cortana content that was created, such as reminders and lists will no longer work in the app, but will continue to be available in Cortana on Windows.
Source: Bleeping Computer