"The teapot is very hot, be careful!" is an accepted other English answer by Duo.
The teapot is very hot, be aware! - Did you use this answer combination?
Dikkat et - be careful! - I have double checked the translation/meaning.
Be aware - farkında olun!
"Çaydanlık çok sıcak, farkında olun!" - The teapot is very hot, be aware!
If you are pouring the tea then "Dikkat et!" is appropriate.
If you are in the kitchen/room near the hot teapot then "farkında olun!" is good.
I'm not saying you are wrong. Duo sets the answer parameters they accept as correct.