N: See apt-secure(8) manpage for repository creation and user configuration details

As said, please post the terminal output. A manpage reference is not very useful, the error code is :slight_smile:

That said, it sounds like your missing some keys. We will know for sure when you post the code. On the off chance I am right, run these lines in terminal (one line at a time).

sudo apt clean
cd /var/lib/apt 
sudo mv lists lists.old
sudo mkdir -p lists/partial
sudo apt update 

And welcome to our forums :grinning:

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