If you are using Dynamics 365 Customer Engagement (CE) in the cloud, then read on...
Microsoft announced that the legacy web client for Dynamics 365 CE won't be available after December 1, 2020. It is recommended that subscribers begin to transition now with the intent to start using the Unified Interface by October 1, 2020. This ensures that any wrinkles are ironed out ahead of time.
To ease a major concern you may have, this transition will not impact the data in your system. Think of it more as a major update.
To prepare our clients we have developed transition documentation to take you through the end to end process.