First Boss Stopped Spawning?

[Sandy]

I went against him a few times trying to learn how to fight and actually remember to block with my newly acquired shell, but after a few deaths the next time I hit the vending machine button and put on the can it just let me leave the area... am I gonna have to restart or is there a way to get him to start showing up again?

[NotASnowman]

Well, he's actually kind of optional. Nephro is not needed to advance the story. If he's stopped spawning it's safe to skip him.

If you want to fight him, I don't know a way to make him spawn again, aside from restarting or playing NG+ after beating the game.

[Sandy]

Eventually I did end up restarting because it bugged me not having earned the shell lol. Thankfully the second time around he didn't stop spawning + I had a bit of practice already so I've fought him then went and explored a bit, ran into the Shellsplitter, and eventually took him out too.