This manga's chapters have been pulled down as a result of the official scanlation.
There is a certain method to tell: If you go into your settings, you can see a drop-down menu labeled, "Unavailable Chapters". If you set it to, "Show (For tracking purposes)", you can see chapters that have been pulled due to scanlation groups. These chapters are unavailable, but (this is speculation) they are still hosted on the server. If you had direct image links, you could still see the individual pages. If a scanlation team chose to come back to Mangadex, they could likely have the staff simply flip some flags related to the chapters and make them available again, saving the trouble and bandwidth of uploading new chapters in place of the removed ones.
However, if you know there were chapters on this site and they still aren't available, it means they have been pulled due to an official scanlation. These chapters have been removed from the servers entirely, as their presence could lead to a legal dispute that Mangadex doesn't want to have to fight. A similar litigation nearly brought this site down, as a "scanlation" group upload rips of official Boruto chapters to this site. VIZ Media, the license holders of Boruto in the US, threatened to bring this whole site down over it. Until Mangadex and VIZ came to an agreement, this entire site was unavailable.
Using the previously discussed technique, one can see that there are not even unavailable chapter markers in this manga. In fact, there is only one chapter... left by Kodansha to get people interested and direct them to the official manga. Such is life. Either way, you know where you can find the chapters.