I use the SDK manager to download some softwares. However, It can’t flash.
Did you run the SDK Manager on a Linux host PC? This is not intended to run on the Jetson. The Jetson must be in recovery mode with the correct USB cable going to the host, and then the host can flash. If your host is a VM, then typically a VM fails to correctly pass through USB…which would be a reason for failing. If you have an actual flash and see some problem named, then you should probably quote whatever error text you saw.
did you use linux computer? windows? mac computer with emulated linux?
did the Jetson device appear as outputs of the command below?
lsusb