This is the trickiest part. Pritom does not maintain an official firmware repository. However, reliable sources exist.
If you have followed every step of this guide and the device remains dead, the issue may be hardware-related: pritom m10 firmware fix
For a deep "firmware fix" using a PC, you would typically use the or SPD Upgrade Tool (depending on whether your M10 uses an Allwinner or Spreadtrum chip), but you must have the specific .img or .pac file provided by Pritom Support. This is the trickiest part