RKDevTool typically requires the device to be in to flash a new image. Entering Maskrom Mode - Radxa Docs
: Most Rockchip-based Single Board Computers (SBCs) only support flashing through a specific OTG-enabled rkdevtool no devices found
This is the "fail-safe" mode. You usually enter it by holding a physical Maskrom button or shorting two specific pins while plugging in the power/USB ( Radxa Docs ). RKDevTool typically requires the device to be in