Yellow Highlighted Cell in Numbers (iCloud on PC)

This is a revival of this forum thread: How do I get rid of a yellow highlite in … - Apple Community

I'm currently having this issue at my Windows workstation. I have no idea what I could have done to cause this, and cannot find any option to remedy the situation.

A cell has a yellow border around it and my name appears when I hover my cursor over the lower right corner. The old forum post appears to have been resolved, but there's no explanation of how or what was done.

If I check this same spreadsheet on my iPhone, the highlight is not there. I've even tried closing and opening the spreadsheet again, but it's still got that one highlighted cell. There isn't even anything important in it besides a date.