A document on Microsofts Site Reads,

“On March 31, 2019, OneDrive music streaming in Groove Music will be retired. Your personal music files will continue to be available in OneDrive. You can keep listening to your music using the OneDrive web player or by downloading your files and playing them in the Groove Music app.”

“Your personal music files will still be available in OneDrive, which you can access online or through the OneDrive application on any supported device. Download your music to your device with the OneDrive app to keep playing it in Groove.”