I run Sierra unsupported on a late 2009 Mac Mini and have had no problems with it until now after trying to uninstall and re-install (unsuccessfully) Skype. The Finder is not working properly. I can't open the Finder window from the Dock nor will Finder - Go work on the menu bar. But Finder - File - New Finder Window does work and I can access Apps from there successully and also from the Dock. Repeated rebooting doesn't work except occasionally for a short time and I've even re-installed Sierra without changing anything. I assume the re-install happened but didn't encounter any setting up procedure though I didn't really expect it. So what's going on with either Finder or the Dock?

Sorry I passed this discussion up. Why I skipped it is the unsupported Sierra. I've found such installs to be troublesome so my advice is to restore to when it worked (even Apple computers must have full backups.) Or bite the big one and install something supported.

commented: Yes. Should we be trying to support something Apple that Apple themselves can't support? +15