The Dynamics 365 for Phones and Tablets application will be deprecated in January 2024. Online users must move to the new Power Apps mobile application. The Power Apps mobile app provides updated capabilities, a modern user experience, and faster load times.
Effectively a user using the old app just needs to uninstall and download the new Power App mobile app from the App Store or Google Play onto an iPhone, iPad, or Android device.
For full instructions on the process and some best practice guidance for users, please click on the below link.