Ensure the MicroSD card is formatted to FAT32. If it still fails, try using an older, lower-capacity card (like 2GB or 4GB), as legacy WonderMedia bootloaders often struggle to read high-capacity SDHC cards during the pre-boot phase.
Check the bottom-left corner of the boot screen for the Build Number to confirm if this version aligns with your device. eken+w70+v20+wm8850+firmware+link
Once the screen displays a message like "Upgrade Successful! Please remove installation media," pull the MicroSD card out of the tablet slot. The tablet will automatically reboot. Ensure the MicroSD card is formatted to FAT32