This keeps popping up every time I open a new Sketchup project even though I click on the accept agreement button.
What is this and how do I stop this from happening?

This looks like an incorrect SketchUp installation. (incorrect permission)

You can try to reinstall SketchUp by right click on a downloaded installer file, chose Run as administrator, and when prompted chose Repair.

Fresh installer file for SketchUp 2023 can be downloaded from here:
Downloading older versions | SketchUp Help

That worked.