Sometimes the problem isn't temperature. If you've done all the above and it's still sour, consider:

• Bean freshness: Old beans lose their sweetness and turn sour. Check your roast date.
• Water quality: Hard water can affect extraction. Try filtered water.
• Ratio: If you're using too little coffee, the brew will be weak and sour. Use 1:15 coffee to water.
• Press quality: A worn seal or cracked cylinder can let grounds through, making the brew taste off.

If none of that helps, it might be the beans themselves. Some origins are naturally brighter and more acidic. That's not a flaw—it's a taste preference. Try a darker roast or a blend with more body.