You downloaded a firmware for a different hardware revision (e.g., DWR-M960A vs DWR-M960B). Fix: Check the sticker on the bottom of the device. "Rev A1" requires different firmware than "Rev B1."

What is the listed on the bottom sticker of your router?

If you cannot find the file for your specific region, contact directly.

Remember: Backup first, verify the checksum, never interrupt the power cycle, and always factory reset after a major version jump.