Same error many people have had lately: https://forum.freecodecamp.org/t/data-analysis-with-python-projects-medical-data-visualizer-heatmap-values/639407/1
Fork this new boilerplate template, and copy your code back in: https://replit.com/@pkdvalis/fcc-2023-Boilerplate-medical-data-visualizer
I haven’t found a root cause but this seems to get around the problem.