Trial of the Empress Not Working?

I've done this twice at different difficulty settings and still no dice.  I think it may just be glitched and you have to fight it a few times to get the unlock, though I have not had any success yet.

I defeated a level 16 Frostback with Even Ground on Nightmare, traveled back and forth between Skyhold and the Hinterlands, no achievement for me either. Interesting note: Dragon Age Keep seems to recognize the achievement. It's not greyed out and locked like the two I know I don't have yet. It's Origin that doesn't recognize it, at least not yet. I'll check back later in case there's some sort of delay.

BTW, I did farm the fade-touched obsidian a few times before checking, so there should have been time for Origin to show the achievement if the Keep did.

@QueenPurpleScrap I didn't check the Keep, but I did have the issue with this achievement clearing on Origin the first time I did it. It did work on my next playthrough (and I think I made sure the dragon was a higher level, just to make extra sure 😛 ), so it wasn't a big deal for me, but I guess it's a bigger issue for people with limited time or motivation to play the game again. 
Origin does sometimes decide to take its time to recognise achievements, too. If it continues being problematic, you could try uninstalling and reinstalling Origin (your games will be safe), sometimes it decides to just be buggy for no apparent reason and doing that can help.

@Leora85, Based on your comment I think I'll wait and see if Origin recognizes the achievement. The game itself must or it couldn't have communicated that to DAKeep. I've got the save in case I need to replay it again. It's not so much a question of time as it is tedium - wouldn't be so bad if I weren't a completionist when it comes to achievements, lol. Meanwhile I'll just go on with the rest of the game.

In any case, thank you for your reply.

Oh don't worry, I get tedium, and being an achievement completionist (though I draw the line at things that try to make me play multiplayer).

I completely misunderstood the 'Trial of the Lovers' one... A whole playthrough wasted making everyone hate me and leave. It said to enter Halamshiral with all followers, I thought it meant enter it with all the followers you had (because everyone else left). 😛 Still, it was worth it to punch Solas in the face. 😉 So then I had to do another playthrough as normal but with that trial still on, still not sure how it was supposed to be a challenge. Making them all throw hissy fits and leave was far more difficult 😛