Differences in heatmap() in base R and Heatmap() in ComplexHeatmap

Question

I have z-score data of differential gene abundances from metagenomic data. When I use the base R heatmap() function I see a heatmap which contains variability in the rows and columns (in such a way that's interesting in terms of our hypothesis). When I use the Heatmap() function from the package ComplexHeatmap, the rows (genes) are virtually the same across each sample. I've varied the clustering distance matrix manually and using built-in correlations but the overall trend of having the same z-scores across the rows is still happening. It's clear I don't understand what's going on under the hood, could someone please explain?