Comment 23 for bug 1523291

I connected the Kobo to the iMac (which has the Micro SD card inserted) and ran Calibre. As usual it said it "Error communicating with device". Then I selected "Restart in debug mode" from the Preferences menu. Calibre restarted and its spinner at bottom right span until is said "Error communicating with device" at which point I quitted Calibre and what I posted was the complete content of the error log that opened after Calibre had quit.

Later I'll try a different procedure. I'll not connect the Kobo to begin with. I'll run Calibre, select "Restart in debug mode" from the Preferences menu, and when Calibre has opened again I'll then connect the Kobo. I'll let you know how that goes.