Display all drawings after an update

1 - Activate iCloud Sync

iPad : Tap the Cloud icon at the bottom of the folder train.
iPhone : Tap the Cloud settings button in the folder browser

Wait a moment and your folders and drawings should display. 

(See screenshot below)

2 - ICloud sync is activated but you still can’t see your drawings in the Sketches app. 

1 / Open Files App
2 / In the Sidebar locations, choose “On my iPad/iPhone"
3 / Look for “Sketches" folder and open it :  your folders and drawings should be there.
4/ Tap on “Select” to select all your folders.
5 /Move all the selected folders to the Sketches Folder in iCloud Drive location.

(See screenshot below)

Wait a moment and open Sketches App, you drawings should be there.

To check that all your drawings are in iCloud Drive.

1 / Open Files App
2 / In the Sidebar locations, choose “iCloud Drive” if you enable Cloud Sync in Sketches app or “On my iPhone/iPad” if not.
3 / Look for “Sketches" folder and open it :  your folders and drawings should be there.