The simple controls are missing for a SharePoint Online document library
When you browse to a SharePoint Online document library in classic Experience, the following simple controls are missing and aren't available for the list:
To work around this problem, use the Default style within the view for the affected library. or Switch to Modern Experience
This problem occurs when you use a view for the document library if the view style is configured to any setting other than Default.
For more information about how to create, change, or delete a view of a list or library, go to Create, change, or delete a view of a list or library.
Still need help? Go to SharePoint Community.