When trying to read Hajime no Ippo, I'm finding that all the early chapters will automatically redirect to the main page of the manga.
To recreate:
1. Go to https://mangadex.org/title/1958/hajime-no-ippo
2. Manually pull up the first chapter and try to go to the next chapter from the reader
You'll see also that the chapter selection will show the most recent chapter instead of the current one. If you expand that drop down, the oldest chapter you'll see is chapter 71. When manually opening chapter 70, you'll also see it show the current chapter as the most recent chapter and trying to go next will also bring you back to the main page, making it safe to assume that it's the same for 1-70.
To recreate:
1. Go to https://mangadex.org/title/1958/hajime-no-ippo
2. Manually pull up the first chapter and try to go to the next chapter from the reader
You'll see also that the chapter selection will show the most recent chapter instead of the current one. If you expand that drop down, the oldest chapter you'll see is chapter 71. When manually opening chapter 70, you'll also see it show the current chapter as the most recent chapter and trying to go next will also bring you back to the main page, making it safe to assume that it's the same for 1-70.