minpac#update() not working on Windows 10 + nvim 0.5.0 about minpac HOT 4 OPEN

I haven't used Neovim, so I'm not sure why this occurs.
What does :set shell? show? I expect shell=C:\Windows\System32\cmd.exe.
Do you set SHELL environment variable?

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You are absolutely right, the shell was pointing to bash. After removing it, :call minpac#update() now throws the following error:

But after continuing with Return, the packages are installed correctly.

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Can you copy&paste the result of :message?

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It is unfortunately just what you see in the screenshot:

Error detected while processing function <SNR>15_HL:
line   43:
E421: Color name or number not recognized: ctermbg= gui=NONE cterm=NONE
E421: Color name or number not recognized: ctermbg= gui=NONE cterm=NONE
E421: Color name or number not recognized: ctermbg= gui=NONE cterm=NONE

I think its a problem with the colorscheme rather than with minpac. For some reason minpac triggers it and that only on Windows.
Edit: I found it, I had to remove let g:gruvbox_sign_column = 'none'.

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