I’ve been having issues in the last month or so with a few things.
Any SketchUp file is taking almost a full minute to open. This is regardless of the file size.
Turning on “Shadows” makes the entire model turn black.
Using the “New Graphics Engine” results in a broken render of the model but if I use the old engine then I have the shadows issue and lose the Ambient Occlusion doesn’t work either.
Have you tried a cold reboot of your computer. Once in a while I see weird graphics with the new graphics engine but a cold reboot of the computer seems to fix it. Simply killing all SketchUp-related processes and reopening SketchUp doesn’t seem to have any impact but a cold reboot does. I just did that a moment ago. I should probably shut down my computer more often than I do.