After firmware upgrade, i got the below

"file transfer failed: receive timeout
invalid upgrade file id"

Any advice ?

I already used the same cable with another routerboard and it worked fine.

Dears, I am facing a critical problem on my RB800 where i am not able to access it via winbox nor via serial. I think the firmware is deleted and i need to install a new one. But the problem that i am not able to access the board using serial connection. Note that the board reboots every 2 minutes. ...