I have also seen this. I have done lots of season 1.1 parties, and sometimes I get ancient coins and sometimes not. May it be that if any of the party members is at the ancient coin cap, the others cannot get any? Just an idea that would match with my observations, but nothing sure.
Thanks for this post! We have been collaborating and testing this issue with ancient coins in coop to try to gather as much data as we can on the issue. Here are some questions we had in our group and thought to try to test against:
Does it matter which dungeon? - Unknown. I consistently earned 0 ancient coins in archive coop battles regardless which season we tried.
Is there just a daily limit on ancient coins? I spent several days into this week (til Wednesday or Thursday) on testing coop archive runs without having done anything solo in the archives. Even when I had earned 0/420 ancient coins for the week, I was consistently earning 0 ancient coins in every coop battle.
Is it consistent across all party members/does one person having earned the limit of ancient coins make a difference? It doesn’t really seem to. Last night we did a test coop run hitting all the different seasons once. At least 2 of us in the party hadn’t yet hit the weekly ancient coins limit. One party member said he earned ancient coins in a handful of the battles but most of the battles still gave him 0 ancient coins, with a total earnings of a just over 100 ancient coins in the time we spent testing. I never earned any ancient coins in any of those battles even though my individual total ancient coins for the week (92/420–all earned only from solo loot tickets) was lower than the amount he was able to accumulate just during the course of our testing.
Does whether or not you earn a kill in the battle affect the ancient coins earned?* It doesn’t seem to. I made kills in some of the battles and didn’t make any kills in other battles. Whether or not I made any kills, I did not earn any ancient coins.
Those are the questions I specifically remembered testing against, but we have have had others that I no longer remember. I hope this additional information will be helpful to the devs.