Turn the TV off, insert the USB, and then hold the Standby/Power button on the remote while turning the power back on. Release it only when the "Software Updating" progress bar appears.
Copy the extracted firmware file (e.g., upgrade_loader.pkg ) directly to the root directory (not inside any folder). Download RSAG7 820 6392 Hisense H50M3300 part10 rar
Place all numbered .rar files in the same folder on your PC. Turn the TV off, insert the USB, and
If the TV works, go to Settings > Support > System Update > Upgrade from USB . Turn the TV off