Revert To Original Firmware Dlink dir-842

Good day everyone.
I have a router Dlink dir-842 c1. I install openwrt and have been using it for a year. I would like to revert to original firmware by looking for some online instructions. When I try, it always fails. Could anyone help me please. I have been looking for the solution almost a day but until now still no luck.
Thank you so much!

Have you tried uploading factory image instead of OpenWRT-factory?

  • Download factory.bin and sysupgrade.bin, as both will be needed (See [Solved] D-LINK DIR-842 C3 installation).

  • Connect your PC to one of the LAN-side ports and configure it to 192.168.0.2 with default gateway configured to 192.168.0.1.

  • Power the router off.

  • Press the reset button and keep it pressed while powering the router on again until the power led blinks about once per second.

  • Go to 192.168.0.1 in your browser. You'll see a quite basic firmware upload form.

  • Upload the factory.bin.

To flash DIR-842 via the recovery (keep reset button pressed during power-on), you need to install the MiddleFirmware first, then continue to flash the latest version:
ftp://ftp.dlink.de/dir/dir-842/driver_software/DIR-842_fw_revc1_313b09-jbma_ALL_multi_20191122.zip

New browsers may cause problems uploading the image via the Web UI at http://192.168.0.1, try using IE 11 etc. instead.