Shouldn’t be an issue, I’m not sure what you’re doing on materials, but space bar is a well known Mac thing: Pressing space bar opens model info, instead of activating the select tool - #5 by kristian
Materials that you make should be saved in ~/Library/Application Support/SketchUp 2016/SketchUp/Materials/What-ever-name-you-gave-the-list. Ours are stored in the app wrapper. Are yours being stored in there somehow? If so, they’re in “/Applications/SketchUp\ 2016/SketchUp.app/Contents/Resources/Content/Materials/”, and you can copy them out and copy them back in. Just make sure you’ve opened SketchUp at least once before doing this or you’ll get security complaints from Apple that an app has been tampered with (and rightly so).