Your computer will not recognize the TV box if it is plugged in normally. You must force it into a flashing mode.
: Getting WiFi (often the fickle SSV6051p chip) or Ethernet to work was a gamble, with developers frequently having to manually "switch" device trees (DTBs) just to turn on a simple LED. The Turning Point: LibreELEC and Armbian rockchip rk3229 custom rom
This guide covers everything you need to know about finding, preparing, and flashing a custom ROM on your RK3229 TV box. Why Flash a Custom ROM on RK3229? Your computer will not recognize the TV box