Showing subcategories of a parent page under subcategory

This question was originally posted one year ago and resolved. In the thread the moderator Mark/t31os made the comment about “display the menu when viewing a single post.” The author of the post apparently worked it out; however his code does not seem to work for me. I’m using Mark’s code from comment #15 and it works great, but I’m very interested in the additional function of showing the menu while viewing a single post. I have searched the forum as well as played with the code and have been unable to find the solution. I’m sure I’m just missing a small snippet of code.

Hopefully, Mark or someone else will see this and be able to provide the missing piece.

Thanks in advance for the help.

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