Why does my correlation matrix show 0 in the TP and FN spaces?

When I predict my test set, I get a good looking correlation matrix, same thing when I predict the train set. But when I predict the entire dataset I get the image below. I was using a voting classifier with different models, decided to use only one model and its the same thing. Took 3 random samples of the dataset (frac=0.3) and the TP and FN values were still zero.As shown here