Although a user has been assigned a document tray, it is not displayed in the Web Client.

A possible cause of this behavior could be that the user is not assigned to the "Public" group.
You can check this in the DocuWare Administration:

If the "Public" group is not assigned here, run the "DWIntegrityCheckTool.exe" program as administrator (C:\Program Files (x86)\DocuWare\Setup Components).
Fill the login window with your system credentials and click on "Analyze":

There should be shown a message like this "User test/635592ac-5c30-480e-b419-c92363811333 is not assigned to 'Public' group of organization 1/Peters Engineering!".
Plaese click on "Repair":

The user is now added to the "Public" group. The document trays are now displayed again for the user in the Web Client.