Can't Create New Section or Section Groups

[kateekw]

I have a section group on my first layer that won't allow me to create
anymore sections or section groups. The section group has one section and
two section groups (2nd tier). One section group has 25 sections the other 1
section (3rd tier). I can create new ones on the first and 3rd tier. What
could be the problem with the second tier?

 

[David Olsen]

I assume you are referring to section groups within a notebook.
Are you using long section/section group names?
From memory there is a limitation on the length of the cumulative name (255
characters?) which you are more likely to run into when using section
groups.

Maybe try out your preferred structure in a test notebook with very short
section/section group names.