still can't make google default search engine in google chrome - what am i missing?

Nine times out of ten it's an extension. Something you installed (often a "pdf converter" or coupon thing) is forcing its own search engine, and Chrome will show the setting as greyed out or just flip it back after a restart. Go to Settings > Search engine, pick Google. If it won't stick, open chrome://extensions and turn everything off, then try again. Turn them back on one at a time and you'll find the culprit. If it says "managed by your organization" and it's your own machine, that's a policy something wrote in - Settings > Reset settings usually clears it.