Yes, the sidebar was visible. And when I restarted the application and tried another long OCR job, the progress did load in the Activity pane, as expected. So my sense is that something goes wrong here if the app has been open for a good period of time. I rarely quit DT3, it sometimes stays open for several days at a time, as it’s one of my most used apps, and though I can’t be fully sure, my sense is that the Activity pane/window misbehavior is more likely to occur when multiple OCR jobs have been queued up. (And, in fact, another problem, though perhaps it is related (?), is if that if I queue up too many OCR jobs, say, a half-dozen or more taking several hours to complete, OCR will eventually fail, all pending OCR jobs will be teminated, and DT3 has to be restarted and the remaining jobs will have to be queued up.)
Running DT3 on an Apple M3 Pro MacBook Pro, Sonoma 14.2.1, 18 GB of RAM.