Hi @kamenriderice,
Welcome to the :qiime2: forum!
Just for your awareness, q2-gneiss is no longer maintained and has been deprecated as of our 2023.9 release. If you're looking for heatmap functionality, I'd recommend checking out q2-vizard, which contains a new suite of visualizations (including a heatmap) and is available within our 2024.10 amplicon distribution (install instructions here).
Hope this helps! Cheers 