OneDrive - Files On Demand (Manually Enable)
An upcoming change by Apple required a change in the One Drive "Files On Demand" feature.
An upcoming macOS update required Microsoft to change the OneDrive "Files On Demand" feature. When OneDrive updates, any files previously marked "Always on this device" will need to be manually switched back to "Always on this device" as shown below (then files will redownload onto your computer).
Click Go then press Option and click Library.
Right click on the OneDrive icon and choose Always Keep On This Device. Alternatively, simply double click the OneDrive icon then right click on Files/Folders you want to sent to Always Keep On This Device.