Global Inbox disappeared from Sorter

In using the Sorter today I noticed that the Global Inbox that is usually in the top left has disappeared, leaving a blank space. I have tried restarting the Sorter but without success. I would appreciate advice on how to get the Global Inbox back in the Sorter. Dragging from DTPO doesn’t seem to work.

Have you restarted your Mac? That seems worth trying before further investigation of the cause of the problem if it persists.

Have you checked [your home folder]/library/application support/DEVONthink Pro 2 if there is still the Inbox folder and the Inbox.dtBase2?

Thanks for the suggestions. I restored, from a Time Machine backup, the Default.sorter file from the DEVONthink Sorter folder in Application Support. That did the trick.