We have Error 0x6100004a on an HP 6968 Printer and have followed all instructions. The problem is on HP's end, as you can see from the update to this video where Restoring to Factory Reset no longer fixes the issue. [Update: HP won't allow YT links]
For the sake of completeness, here's what was tried before the Factory Reset
1. Turned off and on the printer several times (Restart).
2. No paper jam. Looked for paper jams or physical obstructions in all locations including the bottom of the printer.
3. Looked at print-head and ink cartridges.
4. Unplugged printer for over 60 seconds three times (Hard reset)
5. checked for latest update