Disconnect the USB cable. Hold the power button for 10–15 seconds. The first boot after firmware update takes 5–10 minutes (Android optimizing apps). Do not interrupt it.
Obtaining firmware updates can be challenging, especially for devices with obscure or proprietary firmware. In some cases, manufacturers may not provide publicly accessible firmware update links or may require users to contact their support team for assistance. ums5121h10natv firmware update link
Because the ums5121h10natv string refers to the hardware core rather than the specific manufacturer, follow this workflow to find a working update file. Disconnect the USB cable