Hello,
I'm not sure if this is the problem, but I do know that my shark jack does take a moment to boot up. Try this: plug the SharkJack into your computer, and set for arming mode. Then, wait 1 minute (As in 60 seconds) or so for the SJ to fully boot before trying to connect.
Before the SharkJack has fully booted, you won’t actually have an IP address, since the DHCP server hasn’t started, etc.