Stanley Thermos Doesn't Keep Warm, In Three Hours My Drink Gets Lukewarm

I bought the product in Turkey 2 weeks ago, but unfortunately the product makes the boiling water lukewarm in 3 hours, and when I wake up in the morning, I find the tea I put boiled at night cold. Can you please help me, what should I do? The product is supposed to keep water hot, but within three hours, it goes from boiling to lukewarm. it all gets cold by morning. if you can help me troubleshoot or provide guidance on what to do next, I'd appreciate it big time. I've checked the manual, but it hasn't offered a solution. Anyway, I appreciate your assistance in resolving this matter.