What version of SketchUp are you using? Your profile says 2020 Free/Make but there is no such version. If you are using SketchUp 2023, Flip Along was removed from the Context menu. It was replaced with a single Flip command.The toolbar button looks like this.
tb_flip_4800x4800.png
You can still set keyboard shortcuts for Flip Along but they won't be found in a menu.