Possible Clues:

• Nonlearner, proverbially
• It's hard to teach one new tricks, so they say
• Pooch beyond trick-learning years, supposedly
• Proverbial fogy
• Resister of new tricks
• One resistant to new tricks
• Love on line would follow one incapable of innovation
• Unteachable one, it's said
• One whose trick-learning years are behind them
• Hard one to teach, proverbially