Their installer for Mac is not yet aware of SU 2023 and won’t copy the extension files to the right place. I have posted on their site asking when they plan to fix it, but no reply so far.
You can get it working by manually copying the files from SU 2022.
They are found in
MacIntosh HD/Library/Application Support/SketchUp 2022/SketchUp/Plugins
You will need to copy them to
MacIntosh HD/Library/Application Support/SketchUp 2023/SketchUp/Plugins
If that folder doesn’t yet exist, you will need to create it.
Edit: added the MacIntosh HD root to the paths above because many users aren’t aware that is what /Library means.