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Thank you @Slypinball. I was able to connect with Sega JVS board in my NNC cab but I wasn't able to get a video signal via VGA so I connected via HDMI to my LCD TV. I was able to play the story mode for 3 or 4 battles before it started to give me Account error 1, Cerficate error 1 similar errors that you had on your screenshot. What did you do to fix these errors?

I also tried to connect with its dedicated content router but the errors won't go away.

I read this posting by user iloveyourmom at https://forum.arcadeotaku.com/viewtopic.php?t=22977. The guy was able to get around ALL.net connection for his Tekken 6 hardware (Namco 357) by sending his hardware to Japan to have its firmware update to latest version. This works because Tekken 6 ALL.net requirement was removed in later firmware update. The guy also mentioned you can ask Namco to connect your Namco system to ALL.net if you pay a monthly fee and credits purchase.