Thank you everyone for the time and suggestions you took with this question.

It appears this problem seemed from the Sphinx version used during the first build.The documents were built using Sphinx 4.X back in 2020 or so.

I knew this, so I upgraded my Sphinx before trying to publish my updated documents into readthedocs. I believe here is where the problem lies, although I cannot pinpoint precisely where/why, but it may be the case that the the structure and elements of Sphinx 4.X are fully supported/ported to the latest Sphinx version.

Long Story short, I simply rebuilt my documentation from scratch by running a sphinx-quickstart in a new folder and then copying the documentation .rst files and configurations into the new folder.