I believe there is an FN key in your laptop.
There is also somewhere in the numerical keys, something like two squares, imagine one square then another square right on top of that but up and to the left a little. That is what this icon looks like.
Press fn and the key with that logo. THere are 3 options that you toggle like this. One is laptop display only, external monitor only, and display both (not necessarily in that order). So once you get it to display on both post another message if you have problems after or during this process.
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