In the task “Horde Havoc” you are required to get 3* in total using 10 minions. I did two attacks, got 1* in the first attack and 2* in the second attack using 30 minions each time, but after the second attack, I didn’t complete the task.
Maybe it was because after the first attack I needed 1 more star to get the star bonus, so after the 2nd attack, where I got 2* I completed the star bonus for 1* I only got 1* for the task.

Thanks for reading.