Do a Wireshark trace of the scan and see where it goes.
My stab-in-the-dark guess would be that the new Router has a different IP than the old one, so the gateway on the printer is now incorrect, or DHCP is on and something else is using the same IP as the Windows 7 PC. But those are obviously guesses.
If the printer shows the job as completed in the Job Status > Completed Jobs screen, that message comes from a confirmation via SMB to the share. Which means the job should be somewhere.
Port 445 is the right one though, not 139.
Make sure you are scanning by IP address and not host name, because the host name may not be registered in DNS on the new LAN.