How did you create the replit? Did you import it normally from github as it shows on the project page?
I think there’s something wrong with your replit. I would fork it from the boilerplate again and copy your code back in. Here it is: https://replit.com/@freeCodeCamp/fcc-medical-data-visualizer
I did this and I was able to get it to generate a heatmap with values and get rid of that strange [‘–’ , ‘–’] behaviour.