I would guess you’ve accidentally changed the cell type from Markdown to Code, so it’s trying to interpret the markdown as though it was python code. That doesn’t end well.
If restoring doesn’t help, it most likely means you didn’t execute the process correctly: it will not replace an existing file, so you need to rename or delete the original first. Here are the fully detailed instructions.
But you may be able to fix the current one: just click on the malfunctioning cell and use the menu “Cell -> Cell type -> Markdown”.