The solution, posted by a user named "SolderSage_67," was not a driver. It was a confession. SolderSage_67 claimed that HP had silently released a firmware update (version 20241108) that deliberately broke third-party toner cartridge support, but in doing so, it corrupted the USB-to-PC handshake for all cartridges, including genuine ones. The "49 Service Error" was a protest from the printer’s own brain.
It started with a single, cryptic line of text on the printer’s small monochrome display: drivers hp laser mfp 137fnw