2017 MacBook Pro stuck on prohibited symbol, can’t reinstall High Sierra

I was going to sell my 2017 MacBook Pro and I attempted to delete all of my photos off of it and I believe I deleted everything personal who bought it asked for his money back now when I start it up there is a not prohibited symbol 🚫 I’ve tried all the online instructions but I can’t redownload high sierra and am struggling to find a way forward

[Re-Titled by Moderator]

Original Title: Unable to reinstall macOS