Everything's been normal for years. But today, without any sound or warning, every torrent reported "Error: No data found..."
In fact, all the harddrives (4) are fine. And Transmission continue to seed and download -- except if I put in a new torrent, it does not appear anywhere, but it will download.
I am a late 2012 iMac. OS 10.15.7
Transmission 3.00. (I trashed it and downloaded new one: made no difference.)