Earlier today it was working as expected after pressing ctrl-s. Classifying. Then disappeared. Restarted DEVONthink, then restarted macBook. Still empty.
Is there a key I don’t know about that I inadvertently pressed or something to remove the suggested list? Or something to recover?
What’s actually selected in the item list?
Ooops. Actually nothing. Gettin’ old I guess. With all the chat about AI, I thought something besides me took over. My bad. 
Actually, I spoke too soon. Yes, when no documents are selected, then no suggestions appear. In hindsight that’s what I thought I was seeing as you suggested.
However, what I am actually seeing now is some new Inbox PDF+Text documents when selected show nothing in the suggested list. My feeble recollection that in the past there always was suggestions, even if not good ones. But the list allowed me to pick a good one or a couple. Some “see also” doc’s appear at bottom, though. I cannot at this juncture discern a pattern, but something has changed.
Probably not an actionable report. Apologies.
Maybe this document is excluded from see also and/or classifying?
I have two documents I’m looking at. One on the right-mouse-click properties menu suggests a reasonable classification but I would not pick it. The other suggests nothing.
I’ve never deliberately excluded anything from See Also and/or Classifying. Is there a setting to do this that I can’t find?
See Info inspector.
Didn’t know that as never used, actually. Neither of these documents have “exclude” checked.
As I said, I wonder if this an “actionable” thing. Perhaps I just deal with it for the time being. Planning to move to DEVONthink4 on next or following beta release.
Do other or most documents show suggestions?
I just added 6 more PDF+Text files (from a web site which never before showed issue so I don’t think that the root cause) into the Inbox, and all show the same symptom of no suggestions. 2 of the 4 show a suggested target in the “Classify” property-which are pretty much on target.
And other document types, e.g. Markdown or RTF? Or stuff in other databases?
All PDF+Text and all in Global Inbox awaiting dispatch to the right database and group. I have very few Markdown or RTF documents except for those I compose/edit myself–which is vastly a smaller component of my DEVONthink databases compared to PDFs.
While it’s odd it just seemed to be a sudden occurrence with a mysterious cause (self-inflicted?) I’ll cope with this for the time-being and hope this mystery is rectified in DEVONthink4 when I upgrade.
Does it happen using new databases and/or version 3.9.8?
Never saw it 3.9.8 or prior versions. Did not notice with 3.9.9 until just recently. Cannot recall when I upgraded to 3.9.9 but relatively soon after availability.
Are you sure they contain a text layer (i.e. does “convert to text” get you a meaningful output)? I’m asking because nowadays (that refers to DT 4 – but you’re talking about DT3. my bad) even PDFs without a text layer are marked as PDF+Text, apparently if Apple’s Live Text or Vision can detect text in them.
In the end only the indexed text (see e.g. Concordance) matters, no matter whether from a text layer or via Apple’s technologies.
Thanks @chrillek and @cgrunenberg … see first post for screen shot. I toggled on/off a few times (once had seemingly no affect) “Current Database Only” and voilà, back to normal. I haven’t the foggiest. Resolved.
Maybe a rather stupid question but it happened to me once. Are all relevant databases open?
