I have the following data:

# successs # non success

population1 12 2293

population2 82 4926

I ran chi square test on the table above using the tool: http://vassarstats.net/newcs.html. I got the following results: chi square = 14.65 and p-value =0.0001. I interpreted this results as the null hypothesis is strongly rejected and that the difference in population does have a an effect on the success rate (I am not sure if this is the right interpretation). The problem is that the Cramer's V is Nan. I calculated the phi value (chi square / n) and I got a very small number which means that the correlation is not significant (0.002). I am confused by this result because I think the pattern is clear as the probability of success in population one is 3.2 times the probability of success in population two. I searched the web and saw that chi square is not good beyond a data size or that I should use Fisher exact test which I tried without success.

Another point, how can we be so sure about rejecting the null hypothesis and then get a weak association suggesting that there is no correlation.

Your help is highly appreciated.