trial master (ultimatum) not appearing

I have played over 100 maps with the ultimatum encounter and finished it to level 10.
the maps were always t16 and rare.
I also set my atla to higher biss encounter chances in ultimatum.

But the trial master does not appear a single time.

It seems obviously bugged and the promised 30% in the atlas passives wont work at all.

please fix it because it is needed for the challenges

Did you actually complete round 10 or saw that they didn't spawn and moved to next one instead? Was changed this league to not announce when Trialmaster would spawn instead of round 10.

Otherwise I'm not sure. I know I killed at least 10 Trialmasters this league without scarabs.

what do you mean?
i completed round 10 every time and got the rewards dropped afterwards. But i never were teleported to the arena with the trialmaster.