Heroku Exec on Docker container not installing - node.js

Question

Im trying to install Heroku Exec on a Docker container so that I can run scripts through a shell. I cannot access a shell on the container. Ive followed the below linked instructions on using heroku ps:exec with Docker, but get this error when running heroku:ps exec . You can see Ive installed the packages in my dockerfile, and I created a /.profile.d folder in my base /app directory, and added the heroku-exec.sh file and pasted the line of code they wanted. seems like Heroku Exec is not installed or working though.
establishing credentials... error
Heroku Exec is not running!
▸ Could not connect to dyno!
▸ Check if the dyno is running with heroku ps
Heroku Exec with Docker:
https://devcenter.heroku.com/articles/exec#using-with-docker
Dockerfile
FROM node:latest
# update and add all the steps for running with xvfb
RUN apt-get update &&\
apt-get install -yq gconf-service libasound2 libatk1.0-0 libc6 libcairo2 libcups2 libdbus-1-3 \
libexpat1 libfontconfig1 libgcc1 libgconf-2-4 libgdk-pixbuf2.0-0 libglib2.0-0 libgtk-3-0 libnspr4 \
libpango-1.0-0 libpangocairo-1.0-0 libstdc++6 libx11-6 libx11-xcb1 libxcb1 libxcomposite1 \
libxcursor1 libxdamage1 libxext6 libxfixes3 libxi6 libxrandr2 libxrender1 libxss1 libxtst6 \
ca-certificates fonts-liberation libappindicator1 libnss3 lsb-release xdg-utils wget \
xvfb x11vnc x11-xkb-utils xfonts-100dpi xfonts-75dpi xfonts-scalable xfonts-cyrillic x11-apps \
&& apt-get install -y wget gnupg \
&& wget -q -O - https://dl-ssl.google.com/linux/linux_signing_key.pub | apt-key add - \
&& sh -c 'echo "deb [arch=amd64] http://dl.google.com/linux/chrome/deb/ stable main" >> /etc/apt/sources.list.d/google.list' \
&& apt-get update \
&& apt-get install -y google-chrome-stable fonts-ipafont-gothic fonts-wqy-zenhei fonts-thai-tlwg fonts-kacst fonts-freefont-ttf libxss1 \
--no-install-recommends \
&& rm -rf /var/lib/apt/lists/*
RUN apt-get install bash
RUN apt-get install python
RUN apt-get install curl
RUN apt-get install openssh-client
#remove zombie images
ADD https://github.com/Yelp/dumb-init/releases/download/v1.2.2/dumb-init_1.2.2_x86_64 /usr/local/bin/dumb-init
RUN chmod +x /usr/local/bin/dumb-init
ENTRYPOINT ["dumb-init", "--"]
# WORKDIR /app
# using /tmp in order to read/write to container fs as non-root user
WORKDIR /tmp
# add the required dependencies - this breaks the build process for some reason, manually npm install below works
# COPY node_modules /app/node_modules
RUN npm install puppeteer \
# Add user so we don't need --no-sandbox.
# same layer as npm install to keep re-chowned files from using up several hundred MBs more space
&& groupadd -r pptruser && useradd -r -g pptruser -G audio,video pptruser \
&& mkdir -p /home/pptruser/Downloads \
&& chown -R pptruser:pptruser /home/pptruser \
&& npm install express \
&& npm install basic-ftp
# && chown -R pptruser:pptruser /node_modules
# For Heroku exec
RUN rm /bin/sh && ln -s /bin/bash /bin/sh
ADD ./.profile.d /app/.profile.d
EXPOSE 3000
# Run everything after as non-privileged user.
USER pptruser
# USER root
# Finally copy the build application
COPY . .
# make sure we can run without a UI
ENV DISPLAY :99
CMD Xvfb :99 -screen 0 1024x768x16 -nolisten unix & node server.js