It is quite common for flash to succeed and the system will fully boot, but video does not display. It is a guarantee that if the unit is in recovery mode, then ethernet will not ping or otherwise work. Even if a flash succeeded while video failed, one would possibly find ethernet ping works, but login would not work because you have to complete first boot account setup (you cannot use ssh to connect to an account which does not yet exist).
Recovery mode does not itself make any changes, but does put the Jetson into a mode which turns it into a special USB device understood only by the driver package. Nothing else will appear to function in recovery mode. Default is to not be in recovery mode.
If your monitor purely HDMI without adapters? Is there anything unusual about the monitor? Can you describe your monitor and cables? Which release of JetPack/SDKM did you use?
NOTE: To see what is really going on serial console is by far the best tool See: