"Page not found" Regarding "Notes" in Project Navigation


Regarding Notes in Project Navigation
Why do I get [Page not found]?
It looks like the attached image.

・This is a newly launched PJ.
・A month ago, we were in this situation in the middle of another running PJ, and we asked our in-house TechTeam to create a new Notes for Navigation.
・I can see it from Entitiy’s ProjectPage => ALL PROJECT PAGES => All Notes.

Is there any way to deal with this?

Best regards.