I haven’t missed a storm since Tuesday and noticed the same thing. I actually just posted a similar theory in another thread: Elemental Storm Issues - #3 by Draagnakx-area-52
I’ll copy the last bit here for visibility:
This achievement is incredibly problematic and before anyone comes in with the “you should have done it sooner” This achievement never had a reward tied to it and neither did the into the storm meta. There was 0 reason to do this achievement prior to patch 10.2.6. Blizzard only added a reward tied to this achievement after changing it to be this rng fiesta. In it’s current implementation, this achievement is completely unreasonable and I would argue statistically impossible for anyone that sleeps or does not work from home to complete.