Welcome to octave!
Ok what you did will work for most packages. Symbolic is an exception. It requires Python and Python's symbolic package.
If you don't want to install those separately, there is a bundled package for windows.
First, uninstall the symbolic package.
Pkg uninstall symbolic (I think. Check the help)
Then go to
where you can download the latest win-py-bundle
Then manually install it using
Pkg install 'fiilename'
(Make sure your in the same working folder as the downloaded file)
Then things should work
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