This is just some general information since not enough details were given to provide any solid answer.
Often the Jetson is up and running even when video fails…video auto configuration might be the issue. If you use an older 15-pin D-sub VGA monitor this is a guaranteed failure and auto configuration cannot succeed (though you could be very lucky).
JetPack itself is just a front end to flashing and extra package installs. The flash step adds some setup to report its IP address to JetPack once flash completes and the Jetson reboots. If you didnt’ also flash (and lots of people use JetPack to download packages without flashing), then the automatic network address setup will fail and you’ll need to manually enter the IP address.
The first thing to check is if your router sees the Jetson asking through DHCP for an address. This might be a router appliance or your Linux PC acting as a router. You might mention your network setup (router appliance versus PC acting as router). If you see an address, then from your host use ping to see if networking is up. An example which assumes the assigned IP address was 192.168.1.3:
Or ssh to that address:
# Either name/pass of "ubuntu"/"ubuntu" or "nvidia"/"nvidia":
By far the most reliable and unstoppable debug tool would be a serial console (settings 115200 8N1, no hardware flow control). See:
Also beware that many people try to use a VM on the host PC, but VMs don’t work (at least not without either luck or some extra USB configuration…and sometimes not even with that).
If you have some more specific logs or details it would help.