Changes to be made while updating hugo version

My website was built on the version v0.96.0. I want to update my hugo version to v0.120.3. For my table of contents, I had a nested navigation structure that would render the categories upon clicking of sections to show what possible subpages we can navigate to for easier access. But after updating my hugo version this feature is not being rendered. I needed some help figuring out what is the problem? and how I am suppose to go about solving this issue

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