Hearthpwn

Ok well putting aside the possibility that you made a mistake (which is honestly probably still the most likely explanation) Blizzard did mess up once a couple years back meaning a small number of players missed out on legendaries from packs. They acknowledged this and compensated those players with dust but it shows it's possible for mistakes on their to happen.

So my next best guess would be that you pre-purchased the upcoming expansion in that bundle which includes an Uldum legendary somewhere in the middle of those 41 packs. I could see that somehow messing with the pity timer (even though it certainly shouldn't) since an Uldum legendary has been added to your card pool even though it wasn't actually from packs. If that's the case it will likely affect others in the coming days/ weeks and it will be worth letting Blizzard know so they can fix it.

https://hearthstone.gamepedia.com/Card_pack_statistics#Pity_Timer

The most obvious possibility would be that your 41 packs are from more than one set. The pity timer runs separately for each set so if you opened say 10 classic packs and 31 Uldum packs in a row and didn't get a legendary that would make perfect sense.