If you are trying to enter Mask Mode using a reset pin or toothpick, your timing might be off.
Open your serial terminal. Configure:
The BootROM is waiting for a specific file (usually a bootloader or firmware header). You must send it using the correct protocol. Common methods: Bootrom Error Wait For Get Please Check Stb Uart Receive
Important: The file must be sent immediately after powering on the device. Some BootROMs wait only 2–5 seconds. If you are trying to enter Mask Mode