Place the extracted firmware file (often M538_upgrade.bin ) directly into the root directory of the USB—do not put it in a folder.
Official updates from the Akai Professional Downloads or authorized service centers are safer than third-party forum links, which may contain malware or the wrong version for your specific panel. How to Safely Perform a Manual Update Download M538 3840x2160 AKAI AKTV5010 part12 rar
Files ending in .part12.rar are part of a split archive. This means: Place the extracted firmware file (often M538_upgrade