Artillery not doing damage

Game: #7930016

In my game I am playing British Columbia. I did what I usually do: I held off on being too aggressive until I had access to artillery. Normally, Artillery is the answer to taking down troops in entrenched positions. Sometime last night my artillery finally made it into position and I declared war to begin my attack. The bombardment began! That's when things started getting wierd. Normally I'll take at least 1 unit down per bombardment with a few small exceptions. After the first attack finished, nothing happened. After the second, still nothing. I thought this was strange, but maybe it was because I only had the one artillery and the damage was just skewing towards the low end. Another artillery joined about 8 hours later. I've been bombarding the same position now for over 12 hours and not a single unit has died. The troops and buildings aren't taking damage at all.
I'd think maybe artillery was nerfed, but it's still effective in other games I'm playing. If someone can look into this or tell me of some change that would explain it I'd really appreciate it.