My email folders when added are not adding to my folder list

Hey Comcast what is up...I just went to comcast and I am reoganizing my email folders.

to make a transition from my gmail account.   So I started to creat my folders and sub folders

and there is on sensitive folder that I am unable to add a sub folder to...??? I have tried 3 separate time and the folder never adds itself into my subfolder, but when I create the other folders they seem to go right where I want them to go.  Why is this happening.  Sort of like the disappearing folders but not really..   Anyone having this issue?