Press and hold the button on the TV while plugging it back in.
Do you have the for this TV, or are you trying to trigger the update using the physical buttons ? CV338H-C42 Software Download Free - Facebook Download CV338H U42 1366x768 ZEPHIR part1 rar
Installing the wrong firmware or losing power during the flash can permanently "brick" your TV. Ensure the panel resolution (1366x768) matches your screen's specifications. Press and hold the button on the TV
A direct USB Firmware Bios Bin is hosted on a Google Drive link via this forum. Download CV338H U42 1366x768 ZEPHIR part1 rar