High level unit challenge didn't triggered

Product: Command & Conquer: Rivals
Platform:Android Phone
List the specific devices you play with (e.g. iPhone 6s Plus, Samsung Galaxy S7) Samsung Galaxy S9+
OS Version Pie 9.0
What is your Player ID? 1004360509413
What type of issue do you have? Gameplay
How often does the bug occur? Occasionally (10% - 49%)
Summarize your bug High level unit challenge match didn't occur even though all of opponent's unit had 2+levels higer than mine
Steps: How can we find the bug ourselves?
Connection Type Mobile
Please select your region Asia
Country Korea

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This is what I wanna report.

I lost medals. It means that match wasn't determined as challenge battle.

Average level of my army is 7. level cap of diamond league is 11.

So, my average army level can trigger challenge match.

Opponent's average army level is higher than 10.

Difference between average army level is more than 3 levels.

I can't understand why challenge match didn't triggered.