Looks like replit has made some changes in handling dependencies.
Currently the most straightforward way I have found is adding required modules manually in the replit.nix file (it’s hidden, you will need to click three dots at the right of the Files tab and click Show hidden files ). Then add required modules in the deps, for this project it should look like:
deps = [
pkgs.python38Full
pkgs.python38Packages.matplotlib
pkgs.python38Packages.numpy
pkgs.python38Packages.pandas
pkgs.python38Packages.seaborn
];