Cell focus in Numbers

My ancient Macbook is running Monterey 12.7.6, and Numbers 13.1. As up-to-date as they can be.

The problem just started about a week or so ago, so it's not an issue with being updated, me thinks. I'm thinking it's a setting within Numbers itself that perhaps we changed inadvertently.

In years past, selecting one cell did NOT draw a dark green box around the entirety of all cells, and prevent the arrow keys from scrolling thru the cells. Now, the selected cell retains a light green box around it, but using the arrow keys to attempt to move around the sheet highlights the new cells with a light green background, but if I type, it only affects the originally selected (with the mouse) cell.

All accessibility settings are the same on both Macbooks. I suspect it has something to do within Numbers simply because the issue only happens in Numbers. Arrow key operation works just fine when using Excel (or any other program/app).

Yes, because spending $1500 to replace an older macbook is what will fix a software issue? Not a good solution, by ay means.